Fix dark-mode email readability, silent reply failures, and add an IMAP connection watchdog

Dark theme: inbound email HTML intentionally keeps its own inline colors
for fidelity (sanitize-html.ts), but a sender's hardcoded dark text (the
common case) was unreadable once the surrounding chrome went dark. Now
forced to the theme's own text color in dark mode only; light mode keeps
full fidelity as before.

Send button: deliverAgentMessage awaited the outbound email/Telegram send
*before* recording the reply, so a broken mail/bot account (e.g. bad SMTP
creds) made the reply vanish entirely — not sent, not saved, no error
shown — with the API's catch-all masking the real cause as a generic
"Ticket not found". Channel delivery is now best-effort: the reply is
always recorded even if outbound delivery fails, and real errors surface
to the compose box instead of failing silently.

IMAP watchdog: a live IDLE connection has gone quietly unresponsive in
production more than once, with mail landing server-side but never
noticed here and no error ever firing. Added a periodic forced NOOP
round-trip with its own deadline, independent of ImapFlow's internal
socket timeout, that tears down and reconnects a connection that stops
answering.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gh2UXUQUVBWroWEnn1FLFG

src/lib/tickets/delivery.ts

@@ -49,19 +49,30 @@ export async function deliverAgentMessage(params: {
     });
   }
 
+  // Channel delivery (email/Telegram) is best-effort: the agent's reply is
+  // the thing that must never be lost. Previously an SMTP/Telegram failure
+  // here threw straight out of this function, so recordAgentReply below was
+  // never reached — the reply vanished entirely (not recorded, nothing
+  // shown in the thread) and the API route's catch-all turned it into a
+  // misleading "Ticket not found". A broken mail/bot account should degrade
+  // to "reply saved internally, not delivered" — never silent data loss.
   let emailMessageId: string | undefined;
   if (ticket.channel === "email") {
     const context = await getEmailThreadContext(params.ticketId);
     if (context) {
-      emailMessageId = await sendTicketReplyEmail({
-        to: context.customerEmail,
-        subject: context.subject,
-        body: params.body,
-        inReplyTo: context.inReplyTo,
-        attachment: params.attachment
-          ? { filename: params.attachment.filename, content: params.attachment.buffer }
-          : undefined,
-      });
+      try {
+        emailMessageId = await sendTicketReplyEmail({
+          to: context.customerEmail,
+          subject: context.subject,
+          body: params.body,
+          inReplyTo: context.inReplyTo,
+          attachment: params.attachment
+            ? { filename: params.attachment.filename, content: params.attachment.buffer }
+            : undefined,
+        });
+      } catch (err) {
+        console.error(`Failed to send reply email for ticket ${params.ticketId}:`, err);
+      }
     }
   }
 
@@ -79,14 +90,18 @@ export async function deliverAgentMessage(params: {
       where: eq(customers.id, result.ticket.customerId),
     });
     if (customer?.telegramChatId) {
-      if (params.attachment) {
-        await sendTelegramFile(
-          customer.telegramChatId,
-          { buffer: params.attachment.buffer, filename: params.attachment.filename, mimeType: params.attachment.mimeType },
-          params.body,
-        );
-      } else {
-        await sendTelegramMessage(customer.telegramChatId, params.body);
+      try {
+        if (params.attachment) {
+          await sendTelegramFile(
+            customer.telegramChatId,
+            { buffer: params.attachment.buffer, filename: params.attachment.filename, mimeType: params.attachment.mimeType },
+            params.body,
+          );
+        } else {
+          await sendTelegramMessage(customer.telegramChatId, params.body);
+        }
+      } catch (err) {
+        console.error(`Failed to deliver reply via Telegram for ticket ${params.ticketId}:`, err);
       }
     }
   }