security: bandit fixes B310/B324/B110 + QuietHTTPServer (#354)

* security: fix bandit security issues (B310, B324)

- Add usedforsecurity=False to MD5 hash in gateway_watcher.py
- Add URL scheme validation to prevent file:// access in config.py
- Add URL validation to bootstrap.py health check
- Add nosec comments where runtime validation exists

* fix: handle ConnectionResetError gracefully and add debug logging

- Add QuietHTTPServer class to suppress noisy connection reset errors
  caused by clients disconnecting abruptly (fixes log spam from
  'ConnectionResetError: [Errno 54] Connection reset by peer')

- Replace silent 'pass' statements with logger.debug() calls across
  api/auth.py, api/config.py, api/gateway_watcher.py, api/models.py,
  and api/onboarding.py for better observability during troubleshooting

- All tests pass (25 passed in test_regressions.py)

* chore: add debug logging to profiles and routes modules

- Replace silent 'pass' statements with logger.debug() calls in
  api/profiles.py for better error visibility during profile switching
  and module patching

- Add logger initialization to api/routes.py

* security: fix B110 bare except/pass issues (bandit security scan)

- Replace bare except/pass patterns with logger.debug() calls
- Fixes CWE-703 (improper check/handling of exceptional conditions)
- Files affected: routes.py, state_sync.py, streaming.py, workspace.py, server.py
- All tests pass successfully

* security: bandit fixes B310/B324/B110 + QuietHTTPServer (#354)

- api/gateway_watcher.py: MD5 usedforsecurity=False (B324)
- api/config.py, bootstrap.py: URL scheme validation before urlopen (B310)
- 12 files: replace bare except/pass with logger.debug() (B110)
- server.py: QuietHTTPServer suppresses client disconnect log noise
- server.py: fix sys.exc_info() (was traceback.sys.exc_info(), impl detail)
- tests/test_sprint43.py: 19 new tests covering all security fixes
- CHANGELOG.md: v0.50.14 entry; 841 tests total (up from 822)

---------

Co-authored-by: lawrencel1ng <lawrence.ling@global.ntt>
Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>

api/auth.py

@@ -6,12 +6,15 @@ or configuring a password in the Settings panel.
 import hashlib
 import hmac
 import http.cookies
+import logging
 import os
 import secrets
 import time
 
 from api.config import STATE_DIR, load_settings
 
+logger = logging.getLogger(__name__)
+
 # ── Public paths (no auth required) ─────────────────────────────────────────
 PUBLIC_PATHS = frozenset({
     '/login', '/health', '/favicon.ico',
@@ -54,7 +57,7 @@ def _signing_key():
             if len(raw) >= 32:
                 return raw[:32]
         except Exception:
-            pass
+            logger.debug("Failed to read signing key from file, generating new key")
     # Generate a new random key
     key = secrets.token_bytes(32)
     try:
@@ -62,7 +65,7 @@ def _signing_key():
         key_file.write_bytes(key)
         key_file.chmod(0o600)
     except Exception:
-        pass  # key works for this process even if persist fails
+        logger.debug("Failed to persist signing key, using in-memory key only")
     return key