refactor(web): runMutation helper for generic-toast admin handlers (#375)

Wraps the dominant pattern (try { await fn } catch { pushToast(errMessage,
'error') }) for the 5 admin/+page.svelte handlers that surface errMessage
directly: onApprove, onReject, onResolve, onDeleteFile, onDeleteLidarr.

Tighter scope than originally planned — the 3 handlers in
admin/users/+page.svelte (onToggleAutoApprove, onGenerateInvite,
onRevokeInvite) use errCode + verb prefix ("Generate failed: ${code}")
which is structurally different and would change UX wire output if
forced through the helper. Skipping them keeps behavior identical.

The helper SWALLOWS errors so callers no longer need try/finally for
busy-state — `saving = true; await runMutation(...); saving = false;`
is correct because runMutation can't throw.

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

web/src/lib/util/runMutation.ts

@@ -0,0 +1,28 @@
+// Wraps the dominant admin-handler mutation pattern:
+//   try { await fn(); pushToast(success?); }
+//   catch (e) { pushToast(errMessage(e), 'error'); }
+//
+// Errors are SWALLOWED — caller does not need a try/catch. Any
+// `saving = true / saving = false` state flag can sit around the
+// `await runMutation(...)` call without try/finally because the
+// helper never rethrows.
+//
+// Use ONLY for handlers that surface errMessage(e) directly.
+// Handlers that branch on specific error codes (last_admin,
+// password_too_short) or build custom copy with errCode keep
+// their inline catch — wrapping those would obscure intent.
+
+import { errMessage } from '$lib/api/errors';
+import { pushToast } from '$lib/stores/toast.svelte';
+
+export async function runMutation(
+  fn: () => Promise<unknown>,
+  opts: { successMessage?: string } = {}
+): Promise<void> {
+  try {
+    await fn();
+    if (opts.successMessage) pushToast(opts.successMessage);
+  } catch (e) {
+    pushToast(errMessage(e), 'error');
+  }
+}

web/src/routes/admin/+page.svelte

@@ -24,8 +24,9 @@
     type ScanScheduleMode
   } from '$lib/api/admin';
   import { qk } from '$lib/api/queries';
-  import { errCode, errMessage } from '$lib/api/errors';
+  import { errCode } from '$lib/api/errors';
   import { pushToast } from '$lib/stores/toast.svelte';
+  import { runMutation } from '$lib/util/runMutation';
   import type {
     AdminQuarantineRow,
     LidarrRequest,
@@ -119,20 +120,16 @@
   }
 
   async function onApprove(r: LidarrRequest) {
-    try {
+    await runMutation(async () => {
       await approveRequest(r.id);
       await invalidateRequests();
-    } catch (e) {
-      pushToast(errMessage(e), 'error');
-    }
+    });
   }
   async function onReject(r: LidarrRequest) {
-    try {
+    await runMutation(async () => {
       await rejectRequest(r.id);
       await invalidateRequests();
-    } catch (e) {
-      pushToast(errMessage(e), 'error');
-    }
+    });
   }
 
   async function invalidateQuarantine() {
@@ -143,12 +140,10 @@
   }
 
   async function onResolve(row: AdminQuarantineRow) {
-    try {
+    await runMutation(async () => {
       await resolveQuarantine(row.track_id);
       await invalidateQuarantine();
-    } catch (e) {
-      pushToast(errMessage(e), 'error');
-    }
+    });
   }
   async function onDeleteFile(row: AdminQuarantineRow) {
     const key = confirmKey(row.track_id, 'delete-file');
@@ -157,12 +152,10 @@
       return;
     }
     clearConfirm();
-    try {
+    await runMutation(async () => {
       await deleteQuarantineFile(row.track_id);
       await invalidateQuarantine();
-    } catch (e) {
-      pushToast(errMessage(e), 'error');
-    }
+    });
   }
   async function onDeleteLidarr(row: AdminQuarantineRow) {
     const key = confirmKey(row.track_id, 'delete-lidarr');
@@ -171,12 +164,10 @@
       return;
     }
     clearConfirm();
-    try {
+    await runMutation(async () => {
       await deleteQuarantineViaLidarr(row.track_id);
       await invalidateQuarantine();
-    } catch (e) {
-      pushToast(errMessage(e), 'error');
-    }
+    });
   }
 
   // ---- Library scan ----