fix(dnfs): validate token via gateway /whoami with RSA signature verification

- Replace unsafe base64-only decode_token() with HTTP POST to gateway /whoami,
  which performs RSA signature verification and expiry checks internally
- Fail-closed on gateway unreachable: return 503 instead of allowing access
- Add [gateway] config section (url/timeout) with GATEWAY_URL env override
- Add missing @_handle_exp decorator to delete_note and update_note views
- Fix Flask endpoint name collision using @functools.wraps on _handle_exp
- Remove unused base64 import
- Update dnfs.ini with gateway config (http://127.0.0.1:8443/whoami, timeout=5)
- Update docker-compose.yml with GATEWAY_URL and host.docker.internal for containers

dnfs/dnfs.py

@@ -22,6 +22,7 @@ import json
 import configparser
 import urllib.request
 import urllib.error
+import functools
 from typing import Dict, Any
 from security_middleware import apply_security_headers
 from log_client import logs
@@ -292,6 +293,7 @@ def _sp_review_text(title, sp):
 
 def _handle_exp(func):
     '''处理视图函数中抛出的异常，并在日志模块中进行记录'''
+    @functools.wraps(func)
     def wrapper():
         try: return func()
         except DnfsExp as e: