Add body read timeout recovery to IMAP client

Introduce Client wrapper with socket deadline support
Add reconnection logic for body read timeouts
Implement test cases for underflow scenarios
Update orchestrator to handle reconnections

internal/imapx/keepalive.go

@@ -3,8 +3,6 @@ package imapx
 import (
 	"context"
 	"time"
-
-	"github.com/emersion/go-imap/v2/imapclient"
 )
 
 // KeepaliveInterval is how often an otherwise-idle IMAP connection is pinged
@@ -31,7 +29,7 @@ const KeepaliveInterval = 60 * time.Second
 //
 // Keepalive returns when ctx is done or when a NOOP fails — a failed NOOP means
 // the connection is already gone, so there is nothing left to keep alive.
-func Keepalive(ctx context.Context, c *imapclient.Client, interval time.Duration) {
+func Keepalive(ctx context.Context, c *Client, interval time.Duration) {
 	t := time.NewTicker(interval)
 	defer t.Stop()
 	for {