fix(audit-tier-2-routes): manual NextResponse.json error sweep + admin form banners

Two final waves of error-surface hygiene closing the audit's MED §12 +
HIGH §15 + HIGH §17 findings:

* 50 route files swept (61 sites): manual NextResponse.json({error,
  status: 4xx|5xx}) early-returns replaced by typed throws +
  errorResponse(err) at the catch.
  - Super-admin gates (13 sites) use new requireSuperAdmin(ctx, action)
    helper from src/lib/api/helpers.ts so denials hit the audit log.
  - Path-param + body validation 400s become ValidationError throws.
  - 404s become NotFoundError or CodedError('NOT_FOUND') for AI
    feature-flag paths.
  - 11 manual 5xx returns now re-throw so error_events captures the
    request-id (the admin error inspector becomes usable from real
    incidents).
  - website-analytics 200-with-error anti-pattern flipped to 409 +
    UMAMI_NOT_CONFIGURED. 502 upstream paths use UMAMI_UPSTREAM_ERROR.
  - 11 sites intentionally preserved: storage/[token] anti-enumeration
    token-failure paths, webhook-secret 401, "Unknown port" 400 in
    public intake.

* 7 admin forms (roles, users, ports, webhooks, custom-fields,
  document-templates, tags) gain a formatErrorBanner() helper from
  src/lib/api/toast-error.ts that builds a multi-line "Error code / Reference ID"
  banner — the rep can copy the request id when reporting a failed
  save.  Banners get whitespace-pre-line so newlines render.

Test status: 1168/1168 vitest, tsc clean.

Refs: docs/audit-comprehensive-2026-05-05.md MED §12 (auditor-F Issue 1)
+ HIGH §15 (auditor-F Issue 2) + HIGH §17 (auditor-H Issue 2).

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

src/app/api/storage/[token]/route.ts

@@ -21,6 +21,7 @@ import { Readable } from 'node:stream';
 import { NextRequest, NextResponse } from 'next/server';
 
 import { MAX_FILE_SIZE } from '@/lib/constants/file-validation';
+import { errorResponse } from '@/lib/errors';
 import { logger } from '@/lib/logger';
 import { redis } from '@/lib/redis';
 import { FilesystemBackend, getStorageBackend } from '@/lib/storage';
@@ -229,7 +230,7 @@ export async function PUT(
     });
   } catch (err) {
     logger.error({ err, key: payload.k }, 'Storage proxy upload write failed');
-    return NextResponse.json({ error: 'Upload write failed' }, { status: 500 });
+    return errorResponse(err);
   }
 
   return NextResponse.json({ ok: true, key: payload.k, sizeBytes: buffer.length }, { status: 200 });