fix(security): Phase 1 P0 hardening from cross-project audit

Close open uploads, image-proxy SSRF, fail-open AI quotas in production,
auth gaps on app routes, and MCP tenant isolation issues.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/tests/unit/entitlements.test.ts

@@ -142,7 +142,8 @@ describe('entitlements', () => {
       expect(result.reason).toBe('FEATURE_NOT_AVAILABLE');
     });
 
-    it('should fail-open when Redis is down', async () => {
+    it('should fail-open when Redis is down in non-production', async () => {
+      vi.stubEnv('NODE_ENV', 'development');
       mockActiveSubscription('BASIC');
       vi.mocked(redis.get).mockRejectedValue(new Error('Connection refused'));
 
@@ -150,6 +151,17 @@ describe('entitlements', () => {
 
       expect(result.allowed).toBe(true);
     });
+
+    it('should fail-closed when Redis is down in production', async () => {
+      vi.stubEnv('NODE_ENV', 'production');
+      mockActiveSubscription('BASIC');
+      vi.mocked(redis.get).mockRejectedValue(new Error('Connection refused'));
+
+      const result = await canUseFeature('user1', 'semantic_search');
+
+      expect(result.allowed).toBe(false);
+      expect(result.reason).toBe('SERVICE_UNAVAILABLE');
+    });
   });
 
   describe('checkEntitlementOrThrow', () => {