Surface channel delivery failures on agent replies instead of swallowing them

The previous fix made a broken SMTP/Telegram account non-fatal — the
reply gets recorded either way now — but that also made delivery
failures completely invisible: an agent sees their reply "sent"
successfully with no indication the customer never actually received it.
Added messages.deliveryFailed, set whenever the outbound send throws, and
a warning badge on the message bubble so this is now visible instead of
silent.

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

src/lib/tickets/service.ts

@@ -75,6 +75,7 @@ function toMessageDTO(message: typeof messages.$inferSelect, attachments: Attach
     visibility: message.visibility,
     attachments,
     createdAt: message.createdAt.getTime(),
+    deliveryFailed: message.deliveryFailed,
   };
 }
 
@@ -142,6 +143,7 @@ async function appendMessage(params: {
   direction: "in" | "out";
   visibility?: "public" | "internal";
   emailMessageId?: string;
+  deliveryFailed?: boolean;
   attachments?: AttachmentInput[];
 }) {
   const [message] = await db
@@ -155,6 +157,7 @@ async function appendMessage(params: {
       bodyHtml: params.bodyHtml ?? null,
       direction: params.direction,
       visibility: params.visibility ?? "public",
+      deliveryFailed: params.deliveryFailed ?? false,
       emailMessageId: params.emailMessageId,
     })
     .returning();
@@ -398,6 +401,7 @@ export async function recordAgentReply(params: {
   agentName: string;
   body: string;
   emailMessageId?: string;
+  deliveryFailed?: boolean;
   attachments?: AttachmentInput[];
 }) {
   const existing = await db.query.tickets.findFirst({ where: eq(tickets.id, params.ticketId) });
@@ -415,6 +419,7 @@ export async function recordAgentReply(params: {
     body: params.body,
     direction: "out",
     emailMessageId: params.emailMessageId,
+    deliveryFailed: params.deliveryFailed,
     attachments: params.attachments,
   });
 }