feat(admin): manual cleanup of stale tus upload sessions + visibility

Adds an admin-driven sweep on top of the existing 24h auto-expire so
operators can see and reap abandoned `.tus/` sessions without waiting.

- storageJanitor: extract `walkTusDir(predicate)` helper, add
  `getStaleTusInfo` + `cleanupStaleTusSessions(thresholdMs, dryRun)`;
  refactor `cleanupTusStragglers` to delegate while preserving its
  janitor-tick `{ removed }` contract.
- StorageStats gains `staleTusSessions` + `staleTusSize` (fixed 1h
  display threshold).
- New `POST /api/admin/storage/cleanup-tus` route with
  `maxAgeHours` validation (positive finite number, default 1) and
  `dryRun` support; admin-gated.
- StoragePanel: 6th overview card "Stale Uploads" + new cleanup
  subsection mirroring the media-cleanup pattern (preview-then-clean
  with shared result panel styling).
- Tests: 8 new janitor tests covering empty dir, threshold filtering,
  dry-run vs live, oldest-mtime tracking, subdir skipping, and the
  override path on the existing straggler sweep. New
  `routes/admin.test.ts` covers auth/admin gates, validation (zero,
  negative, NaN), default `maxAgeHours`, dry-run vs live unlink.
- Docs: `uploads.md` §Janitor expanded to the full lifecycle (cancel
  DELETE, discard DELETE, auto-expire, straggler sweep, admin route);
  `admin.md` Storage Management updated with the new endpoint and
  StorageStats fields.

packages/server/src/routes/admin.ts

@@ -2,7 +2,7 @@ import type { FastifyInstance } from 'fastify';
 import crypto from 'crypto';
 import { eq, like, or, and, ne, sql, isNull, isNotNull, gte, lte, asc, desc } from 'drizzle-orm';
 import { authenticate, requireAdmin, hashPassword } from '../utils/auth.js';
-import { getStorageStats, getOrphanedFiles, cleanupStorage, cleanupOldMedia } from '../utils/storageJanitor.js';
+import { getStorageStats, getOrphanedFiles, cleanupStorage, cleanupOldMedia, cleanupStaleTusSessions } from '../utils/storageJanitor.js';
 import { getDb, schema } from '../db/index.js';
 import { connectionManager } from '../ws/handler.js';
 import { tombstoneUser, collectDeletionBroadcastTargets } from '../utils/userDeletion.js';
@@ -74,6 +74,32 @@ export async function adminRoutes(app: FastifyInstance): Promise<void> {
     }
   });
 
+  // POST /api/admin/storage/cleanup-tus — admin-driven sweep of stale tus
+  // upload sessions. Defaults: maxAgeHours=1 (matches the staleTusSessions
+  // display threshold), dryRun=false. Per-file unlink errors are surfaced via
+  // CleanupResult.errors. No DB rows touched — `.tus/` is filesystem-only.
+  app.post<{ Body: { maxAgeHours?: number; dryRun?: boolean } }>('/api/admin/storage/cleanup-tus', { preHandler: [authenticate, requireAdmin] }, async (request, reply) => {
+    try {
+      const rawAge = request.body?.maxAgeHours;
+      const maxAgeHours = rawAge === undefined ? 1 : Number(rawAge);
+      if (!Number.isFinite(maxAgeHours) || maxAgeHours <= 0) {
+        return reply.code(400).send({ error: 'maxAgeHours must be a positive finite number', statusCode: 400 });
+      }
+      const dryRun = request.body?.dryRun ?? false;
+      const thresholdMs = maxAgeHours * 60 * 60 * 1000;
+      const result = cleanupStaleTusSessions(thresholdMs, dryRun);
+      return reply.code(200).send({
+        dryRun,
+        deletedFiles: result.deletedFiles,
+        freedBytes: result.freedBytes,
+        deletedAttachmentRecords: 0,
+        errors: result.errors,
+      });
+    } catch (err: any) {
+      return reply.code(500).send({ error: `Tus cleanup failed: ${err.message}`, statusCode: 500 });
+    }
+  });
+
   // ─── User Management ────────────────────────────────────────────────────
 
   // GET /api/admin/users — paginated user list with search