fix(audit-tier-2): error-surface hygiene — toastError + CodedError sweep

Two mechanical sweeps closing the audit's HIGH §16 + MED §11 findings:

* 38 client components / 56 toast.error sites converted to
  toastError(err) so the new admin error inspector becomes usable from
  user-reported issues — every failed inline-edit, save, send, archive,
  upload, etc. now carries the request-id + error-code (Copy ID action).
* 26 service files / 62 bare-Error throws converted to CodedError or
  the existing AppError subclasses.  Adds new error codes:
  DOCUMENSO_UPSTREAM_ERROR (502), DOCUMENSO_AUTH_FAILURE (502),
  DOCUMENSO_TIMEOUT (504), OCR_UPSTREAM_ERROR (502),
  IMAP_UPSTREAM_ERROR (502), UMAMI_UPSTREAM_ERROR (502),
  UMAMI_NOT_CONFIGURED (409), and INSERT_RETURNING_EMPTY (500) for
  post-insert returning-empty guards.
* Five vitest assertions updated to match the new user-facing wording
  (client-merge "already been merged", expense/interest "couldn't find
  that …", documenso "signing service didn't respond").

Test status: 1168/1168 vitest, tsc clean.

Refs: docs/audit-comprehensive-2026-05-05.md HIGH §16 (auditor-H Issue 1)
+ MED §11 (auditor-G Issue 1).

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

src/lib/services/gdpr-export.service.ts

@@ -18,7 +18,7 @@ import { db } from '@/lib/db';
 import { gdprExports, type GdprExport } from '@/lib/db/schema/gdpr';
 import { clients, clientContacts } from '@/lib/db/schema/clients';
 import { ports } from '@/lib/db/schema/ports';
-import { NotFoundError, ValidationError } from '@/lib/errors';
+import { CodedError, NotFoundError, ValidationError } from '@/lib/errors';
 import { logger } from '@/lib/logger';
 import { getStorageBackend, presignDownloadUrl } from '@/lib/storage';
 import { getQueue } from '@/lib/queue';
@@ -82,7 +82,10 @@ export async function requestGdprExport(input: RequestExportInput): Promise<Requ
       status: 'pending',
     })
     .returning();
-  if (!row) throw new Error('Failed to create export row');
+  if (!row)
+    throw new CodedError('INSERT_RETURNING_EMPTY', {
+      internalMessage: 'GDPR export row insert returned no row',
+    });
 
   void createAuditLog({
     userId: input.requestedBy,
@@ -153,9 +156,9 @@ export async function processGdprExportJob(input: ProcessJobInput): Promise<void
     const buffer = await done;
 
     if (buffer.length > MAX_BUNDLE_BYTES) {
-      throw new Error(
-        `GDPR bundle exceeded ${MAX_BUNDLE_BYTES} bytes (got ${buffer.length}); refusing to upload`,
-      );
+      throw new CodedError('INTERNAL', {
+        internalMessage: `GDPR bundle exceeded ${MAX_BUNDLE_BYTES} bytes (got ${buffer.length}); refusing to upload`,
+      });
     }
 
     const port = await db.query.ports.findFirst({ where: eq(ports.id, input.portId) });