fix(admin-api): accept slug or UUID on per-app endpoints

The Queues tab at /admin/apps/default/queues was returning
"Cannot parse `app_id` with value `default`: UUID parsing failed".
27 admin endpoints across 6 files used strict `Path<AppId>` instead
of the canonical `Path<String>` + `resolve_app()` pattern from
app_repo.rs:34. Working endpoints (apps, app_members, users_admin)
all use the lenient pattern; this commit brings the remaining 6
files into line:

- queues_api.rs       — 2 handlers
- files_api.rs        — 2 handlers
- secrets_api.rs      — 3 handlers
- topics_api.rs       — 4 handlers
- dead_letters_api.rs — 5 handlers
- triggers_api.rs     — 10 handlers

The handler bodies (authz, repo calls) are unchanged; only the path
extractor and the per-file `ensure_app_exists` helper (now renamed
`resolve_app`) move. Lib tests updated to pass `.to_string()` at
the call site (Path now takes String, not AppId).

email_inbound_api.rs deliberately stays strict-UUID — it's a public
webhook receiver consumed by external providers, not by the
slug-based dashboard.

Adds Playwright spec `dashboard/tests/e2e/navigation/tabs.spec.ts`
covering every per-app tab (queues, files, dead-letters, users,
invitations, plus the main page hosting triggers/secrets/topics)
with a negative assertion against the "Cannot parse" error text
plus a focused regression test for the original queues report.

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

crates/manager-core/src/dead_letters_api.rs

@@ -114,10 +114,10 @@ impl From<DeadLetterRow> for DeadLetterDto {
 async fn list(
     State(s): State<DeadLettersState>,
     Extension(principal): Extension<Principal>,
-    Path(app_id): Path<AppId>,
+    Path(id_or_slug): Path<String>,
     Query(q): Query<ListQuery>,
 ) -> Result<Json<ListResponse>, DeadLettersApiError> {
-    ensure_app(&*s.apps, app_id).await?;
+    let app_id = resolve_app(&*s.apps, &id_or_slug).await?;
     require(
         s.authz.as_ref(),
         &principal,
@@ -136,9 +136,9 @@ async fn list(
 async fn count(
     State(s): State<DeadLettersState>,
     Extension(principal): Extension<Principal>,
-    Path(app_id): Path<AppId>,
+    Path(id_or_slug): Path<String>,
 ) -> Result<Json<CountResponse>, DeadLettersApiError> {
-    ensure_app(&*s.apps, app_id).await?;
+    let app_id = resolve_app(&*s.apps, &id_or_slug).await?;
     require(
         s.authz.as_ref(),
         &principal,
@@ -152,9 +152,9 @@ async fn count(
 async fn detail(
     State(s): State<DeadLettersState>,
     Extension(principal): Extension<Principal>,
-    Path((app_id, dl_id)): Path<(AppId, DeadLetterId)>,
+    Path((id_or_slug, dl_id)): Path<(String, DeadLetterId)>,
 ) -> Result<Json<DeadLetterDto>, DeadLettersApiError> {
-    ensure_app(&*s.apps, app_id).await?;
+    let app_id = resolve_app(&*s.apps, &id_or_slug).await?;
     require(
         s.authz.as_ref(),
         &principal,
@@ -175,9 +175,9 @@ async fn detail(
 async fn replay(
     State(s): State<DeadLettersState>,
     Extension(principal): Extension<Principal>,
-    Path((app_id, dl_id)): Path<(AppId, DeadLetterId)>,
+    Path((id_or_slug, dl_id)): Path<(String, DeadLetterId)>,
 ) -> Result<StatusCode, DeadLettersApiError> {
-    ensure_app(&*s.apps, app_id).await?;
+    let app_id = resolve_app(&*s.apps, &id_or_slug).await?;
     // Authz handled inside the service via SdkCallCx.
     let cx = admin_cx(app_id, &principal);
     s.service
@@ -190,10 +190,10 @@ async fn replay(
 async fn resolve(
     State(s): State<DeadLettersState>,
     Extension(principal): Extension<Principal>,
-    Path((app_id, dl_id)): Path<(AppId, DeadLetterId)>,
+    Path((id_or_slug, dl_id)): Path<(String, DeadLetterId)>,
     Json(body): Json<ResolveBody>,
 ) -> Result<StatusCode, DeadLettersApiError> {
-    ensure_app(&*s.apps, app_id).await?;
+    let app_id = resolve_app(&*s.apps, &id_or_slug).await?;
     let cx = admin_cx(app_id, &principal);
     s.service
         .resolve(&cx, dl_id, &body.reason)
@@ -221,12 +221,12 @@ fn admin_cx(app_id: AppId, principal: &Principal) -> SdkCallCx {
     }
 }
 
-async fn ensure_app(apps: &dyn AppRepository, app_id: AppId) -> Result<(), DeadLettersApiError> {
-    apps.get_by_id(app_id)
+async fn resolve_app(apps: &dyn AppRepository, ident: &str) -> Result<AppId, DeadLettersApiError> {
+    crate::app_repo::resolve_app(apps, ident)
         .await
         .map_err(|e| DeadLettersApiError::Backend(e.to_string()))?
-        .ok_or_else(|| DeadLettersApiError::AppNotFound(app_id.to_string()))?;
-    Ok(())
+        .map(|l| l.app.id)
+        .ok_or_else(|| DeadLettersApiError::AppNotFound(ident.to_string()))
 }
 
 fn map_service_err(e: picloud_shared::DeadLetterError) -> DeadLettersApiError {