feat(v1.1.1-dead-letters): dashboard badge + list view

Design notes §4 makes the dashboard surface load-bearing — with no
default DL handler, users wouldn't know dead letters exist
otherwise.

New route: `apps/[slug]/dead-letters/+page.svelte` — list view
columns per the design notes:
- `created_at`, `source`, `op`, `script_id`, `attempt_count`,
  `first/last_attempt_at`, `last_error` (truncated; clickable)
- per-row Replay + Mark resolved buttons
- expandable row detail panel showing full payload (JSON) +
  full last_error
- unresolved-only filter (default on); refresh button

Per-app detail page (`apps/[slug]/+page.svelte`) grows a "Dead
letters" link in the tabs nav, with a red unresolved-count pill
when > 0. Loaded in parallel with the existing app loaders so it
doesn't slow the page.

Apps list (`apps/+page.svelte`) shows the same red pill next to
each app's name when its unresolved count > 0. Counts fetched in
parallel after the apps list lands; failures here are non-fatal
(just no badge).

API client wiring: `api.deadLetters.{count,list,get,replay,resolve}`
mirrors the v1.1.1 admin endpoints. `DeadLetterRow` type added to
the dashboard's API shape declarations.

dashboard's svelte-check passes (369 files, 0 errors, 0 warnings).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/lib/api.ts

@@ -186,6 +186,23 @@ export interface UpdateScriptInput {
 	sandbox?: ScriptSandbox;
 }
 
+export interface DeadLetterRow {
+	id: string;
+	app_id: string;
+	source: string;
+	op: string;
+	trigger_id: string | null;
+	script_id: string | null;
+	payload: unknown;
+	attempt_count: number;
+	first_attempt_at: string;
+	last_attempt_at: string;
+	last_error: string;
+	created_at: string;
+	resolved_at: string | null;
+	resolution: 'replayed' | 'ignored' | 'handled_by_script' | 'handler_failed' | null;
+}
+
 export interface ExecutionResult {
 	status: number;
 	headers: Record<string, string>;
@@ -516,6 +533,37 @@ export const api = {
 			)
 	},
 
+	deadLetters: {
+		count: (idOrSlug: string) =>
+			adminRequest<{ unresolved: number }>(
+				`/api/v1/admin/apps/${encodeURIComponent(idOrSlug)}/dead_letters/count`
+			),
+		list: (idOrSlug: string, opts: { unresolved?: boolean; limit?: number; offset?: number } = {}) => {
+			const params = new URLSearchParams();
+			if (opts.unresolved) params.set('unresolved', 'true');
+			if (opts.limit !== undefined) params.set('limit', String(opts.limit));
+			if (opts.offset !== undefined) params.set('offset', String(opts.offset));
+			const qs = params.toString();
+			return adminRequest<{ dead_letters: DeadLetterRow[] }>(
+				`/api/v1/admin/apps/${encodeURIComponent(idOrSlug)}/dead_letters${qs ? `?${qs}` : ''}`
+			);
+		},
+		get: (idOrSlug: string, dlId: string) =>
+			adminRequest<DeadLetterRow>(
+				`/api/v1/admin/apps/${encodeURIComponent(idOrSlug)}/dead_letters/${dlId}`
+			),
+		replay: (idOrSlug: string, dlId: string) =>
+			adminRequest<null>(
+				`/api/v1/admin/apps/${encodeURIComponent(idOrSlug)}/dead_letters/${dlId}/replay`,
+				{ method: 'POST' }
+			),
+		resolve: (idOrSlug: string, dlId: string, reason: string) =>
+			adminRequest<null>(
+				`/api/v1/admin/apps/${encodeURIComponent(idOrSlug)}/dead_letters/${dlId}/resolve`,
+				{ method: 'POST', body: JSON.stringify({ reason }) }
+			)
+	},
+
 	execute: async (
 		id: string,
 		body: unknown,