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>

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}