feat: pattern/creator grouping, notification UI, failure alerts

Pattern grouping (Signal 3):
- Extract YYYY-MM dates, month names, and project prefixes from filenames
- Auto-group packages sharing the same pattern within a channel
- Groups created with groupingSource=AUTO_PATTERN

Creator grouping (Signal 4):
- Auto-group 3+ ungrouped packages from the same creator within a channel
- Runs after pattern grouping as lowest-priority automatic signal

Notification UI:
- Add NotificationBell component to header with unread badge
- Popover panel shows recent notifications with severity icons
- Mark individual or all notifications as read
- Polls every 30 seconds for updates

Failure notifications:
- Upload/download failures now create SystemNotification records
- Visible in the notification bell alongside hash mismatch alerts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

worker/src/db/queries.ts

@@ -608,3 +608,25 @@ export async function createTimeWindowGroup(input: {
 
   return group.id;
 }
+
+export async function createAutoGroup(input: {
+  sourceChannelId: string;
+  name: string;
+  packageIds: string[];
+  groupingSource: "AUTO_TIME" | "AUTO_PATTERN" | "AUTO_ZIP" | "AUTO_CAPTION";
+}): Promise<string> {
+  const group = await db.packageGroup.create({
+    data: {
+      sourceChannelId: input.sourceChannelId,
+      name: input.name,
+      groupingSource: input.groupingSource,
+    },
+  });
+
+  await db.package.updateMany({
+    where: { id: { in: input.packageIds } },
+    data: { packageGroupId: group.id },
+  });
+
+  return group.id;
+}