feat(web): scrollable Forecast log with fixed height

Cap the log panel at ~216px with a thin themed scrollbar so a long
forecast history does not stretch the page.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -0,0 +1,9 @@
+# Arduino
+
+A collection of Arduino / ESP microcontroller projects.
+
+## Projects
+
+- **[WeatherPredictor](WeatherPredictor/)** — autonomous barometric weather
+  station on a Wemos D1 mini (ESP8266): local Zambretti forecast, TFT display
+  and a self-hosted web interface. See its [README](WeatherPredictor/README.md).

WeatherPredictor/README.md

@@ -0,0 +1,116 @@
+# Weather Predictor
+
+An autonomous **barometric weather station** built on a Wemos D1 mini (ESP8266).
+It reads atmospheric pressure and temperature, keeps accurate battery-backed
+time, and predicts near-term local weather entirely on-device using the
+**Zambretti algorithm** — no internet forecast service required. Readings and
+the forecast are shown on a small TFT and on a self-hosted web interface styled
+as a barometer instrument.
+
+![The Weather Predictor web interface, live from the station](WeatherPredictor.jpg)
+
+## Features
+
+- **Local Zambretti forecast** from the 3-hour sea-level pressure trend (rising / steady / falling), adjusted for season.
+- **On-device TFT screen** (160×80): time, date, pressure with trend arrow, temperature, a scaled weather icon, and the station's Wi-Fi/IP.
+- **Web interface** served from the device (no external CDNs, works offline):
+  - live barometer dial with a needle and a "set hand" ghost at the pressure 3 h ago;
+  - barograph of pressure & temperature with labelled axes;
+  - **forecast change log**;
+  - settings with **city presets** and a UTC-offset time-zone picker.
+- **Persistence** in LittleFS: settings, pressure history, and the forecast log all survive reboots.
+- **Wi-Fi provisioning** via WiFiManager (captive portal — no credentials in code) and **NTP** time sync to the DS3231.
+
+## Hardware
+
+| Component | Part | Bus / notes |
+|-----------|------|-------------|
+| MCU | Wemos D1 mini (ESP8266, 4 MB flash) | — |
+| Pressure & temperature | BMP180 (GY-68) | I²C, addr `0x77` |
+| Real-time clock | DS3231 (HW-022, battery-backed) | I²C, addr `0x68` |
+| Display | 0.96" 80×160 TFT, ST7735S | 4-wire SPI, run landscape 160×80 |
+
+### Wiring
+
+The display uses hardware SPI; the two I²C modules share one bus.
+
+| Signal | Wemos pin | GPIO |
+|--------|-----------|------|
+| TFT CS | D8 | 15 |
+| TFT DC | D3 | 0 |
+| TFT RST | D4 | 2 |
+| TFT SDA (MOSI) | D7 | 13 |
+| TFT SCL (SCK) | D5 | 14 |
+| TFT BLK (backlight) | D2 | 4 |
+| I²C SDA (BMP180 + DS3231) | D6 | 12 |
+| I²C SCL (BMP180 + DS3231) | D1 | 5 |
+
+All modules run on 3.3 V / GND. I²C is started with `Wire.begin(D6 /*SDA*/, D1 /*SCL*/)`.
+
+## Build & flash (Arduino IDE)
+
+1. Install the **ESP8266** board package; select board **"LOLIN(WEMOS) D1 R2 & mini"**.
+2. Set **Tools → Flash Size** to a layout with a filesystem, e.g. **4MB (FS:2MB)**.
+3. Install libraries via Library Manager:
+   *Adafruit GFX*, *Adafruit ST7735 and ST7789*, *Adafruit BMP085*, *RTClib*,
+   *ArduinoJson* (v7.x), *WiFiManager* (by tzapu).
+   `ESP8266WiFi`, `ESP8266WebServer`, `LittleFS`, `Wire`, `SPI`, `time` ship with the core.
+4. Open `WeatherPredictor/WeatherPredictor.ino` and upload.
+
+## First run
+
+1. On first boot the device opens a Wi-Fi access point **`WeatherPredictor-Setup`**.
+   Join it from a phone and pick your network in the captive portal.
+2. After connecting, the device syncs time over NTP and writes it to the DS3231.
+3. The screen and Serial (115200) print the station's IP — open `http://<ip>/`.
+4. The forecast shows **"Collecting data…"** until ~3 h of pressure history exists;
+   that is expected — the Zambretti method needs a trend before its first call.
+
+Set your **altitude** in the web settings (or pick a city preset): sea-level
+pressure — and therefore the forecast — depends on it (~0.12 hPa per metre).
+
+## REST API
+
+| Endpoint | Method | Returns |
+|----------|--------|---------|
+| `/` | GET | Web UI |
+| `/api/current` | GET | time, pressure (abs + sea level), temperature, trend, forecast |
+| `/api/history` | GET | recent pressure/temperature samples |
+| `/api/forecasts` | GET | forecast change log (newest first) |
+| `/api/settings` | GET / POST | altitude, time-zone offset, coordinates |
+
+## Project structure
+
+```
+WeatherPredictor/
+  WeatherPredictor.ino   scheduler; wires the modules together
+  config.h               pins, addresses, intervals, defaults
+  state.h                shared current-readings struct
+  sensors.*              BMP180 read + sea-level conversion
+  rtc_time.*             DS3231 read/set + NTP sync
+  display_ui.*           ST7735 rendering + weather icons
+  forecast.*             Zambretti forecast + trend classification
+  history.*              pressure ring buffer + LittleFS persistence
+  flog.*                 forecast change log
+  app_settings.*         settings struct + LittleFS JSON
+  net.*                  WiFiManager connection
+  web_server.*           HTTP server + REST API
+  web_page.h             web UI (HTML/CSS/JS) in PROGMEM
+  docs/superpowers/      design spec and implementation plan
+```
+
+## Notes & gotchas
+
+- **BGR panel:** this 0.96" ST7735S has red/blue swapped, so colours are built
+  R/B-exchanged in `display_ui.cpp`. If your panel looks wrong, adjust there
+  (and the `invertDisplay` / `setRotation` in `displayBegin()`).
+- **Restrictive networks:** on some LANs the router does not resolve external
+  hostnames, so NTP uses hard-coded Cloudflare/Google anycast IPs instead of
+  names. Such networks may also block SSH.
+- **Flash wear:** history is flushed every 15 min and the forecast log only on
+  change, so LittleFS wear leveling keeps flash life at years/decades.
+
+## Credits
+
+Zambretti forecast constants and lookup tables adapted from
+[G6EJD's ESP Zambretti forecaster](https://github.com/G6EJD/ESP32_Weather_Forecaster_TN061).

WeatherPredictor/WeatherPredictor.ino

@@ -88,6 +88,15 @@ void loop() {
     tSample = now;
     sampleNow();
     displayRender(g_state);
+    Serial.printf("heap=%u maxblock=%u\n", ESP.getFreeHeap(), ESP.getMaxFreeBlockSize());
+    // Safety net: if the largest contiguous block gets too small, the TCP stack
+    // can no longer send responses. Persist and reboot to defragment.
+    if (ESP.getMaxFreeBlockSize() < 6000) {
+      Serial.println(F("Low memory -> saving history and restarting"));
+      historySave();
+      delay(50);
+      ESP.restart();
+    }
   }
 
   if (now - tHistory >= HISTORY_INTERVAL_MS) {

WeatherPredictor/web_page.h

@@ -103,7 +103,11 @@ static const char INDEX_HTML[] PROGMEM = R"HTML(
   .cap{color:var(--muted); font-size:.74rem; letter-spacing:.06em}
 
   /* Forecast log */
-  .log{list-style:none; margin:2px 0 0; padding:0}
+  .log{list-style:none; margin:2px 0 0; padding:0 8px 0 0; max-height:216px; overflow-y:auto;
+       scrollbar-width:thin; scrollbar-color:var(--line) transparent}
+  .log::-webkit-scrollbar{width:8px}
+  .log::-webkit-scrollbar-thumb{background:var(--line); border-radius:8px}
+  .log::-webkit-scrollbar-track{background:transparent}
   .log li{display:flex; align-items:center; gap:13px; padding:12px 0; border-top:1px solid var(--line)}
   .log li:first-child{border-top:0}
   .log .dot{width:9px; height:9px; border-radius:50%; flex:0 0 auto}

WeatherPredictor/web_server.cpp

@@ -27,41 +27,44 @@ static void handleCurrent() {
   doc["haveTrend"] = g_state.haveTrend;
   doc["forecast"]  = g_state.haveTrend ? g_state.forecast.text : "Collecting data...";
   doc["category"]  = g_state.haveTrend ? categoryShort(g_state.forecast.category) : "...";
+  doc["heap"]      = ESP.getFreeHeap();       // for monitoring memory health
   String out;
   serializeJson(doc, out);
   server.send(200, "application/json", out);
 }
 
+// Streamed (chunked) so we never build a large String/JsonDocument on the heap.
 static void handleHistory() {
-  JsonDocument doc;
+  server.setContentLength(CONTENT_LENGTH_UNKNOWN);
-  JsonArray arr = doc.to<JsonArray>();
+  server.send(200, "application/json", "");
+  server.sendContent("[");
+  char buf[80];
   int n = historyCount();
   for (int i = 0; i < n; i++) {
     Sample s = historyGet(i);
-    JsonObject o = arr.add<JsonObject>();
+    snprintf(buf, sizeof(buf), "%s{\"t\":%lu,\"msl\":%.1f,\"temp\":%.1f}",
-    o["t"]    = s.epoch;
+             i ? "," : "", (unsigned long)s.epoch, s.mslHpa, s.tempC);
-    o["msl"]  = s.mslHpa;
+    server.sendContent(buf);
-    o["temp"] = s.tempC;
   }
-  String out;
+  server.sendContent("]");
-  serializeJson(doc, out);
-  server.send(200, "application/json", out);
 }
 
+// Streamed (chunked). Forecast phrases contain no quotes/backslashes, so they
+// are safe to embed directly in JSON.
 static void handleForecasts() {
-  JsonDocument doc;
+  server.setContentLength(CONTENT_LENGTH_UNKNOWN);
-  JsonArray arr = doc.to<JsonArray>();
+  server.send(200, "application/json", "");
+  server.sendContent("[");
+  char buf[128];
   int n = flogCount();
-  for (int i = n - 1; i >= 0; i--) {          // newest first
+  for (int i = n - 1, first = 1; i >= 0; i--, first = 0) {   // newest first
     FcastEntry e = flogGet(i);
-    JsonObject o = arr.add<JsonObject>();
+    snprintf(buf, sizeof(buf), "%s{\"t\":%lu,\"cat\":\"%s\",\"text\":\"%s\"}",
-    o["t"]    = e.epoch;
+             first ? "" : ",", (unsigned long)e.epoch,
-    o["cat"]  = categoryShort((WxCategory)e.cat);
+             categoryShort((WxCategory)e.cat), forecastTextForLetter(e.letter));
-    o["text"] = forecastTextForLetter(e.letter);
+    server.sendContent(buf);
   }
-  String out;
+  server.sendContent("]");
-  serializeJson(doc, out);
-  server.send(200, "application/json", out);
 }
 
 static void handleGetSettings() {