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>

server.py

@@ -3,11 +3,16 @@ Hermes Web UI -- Main server entry point.
 Thin routing shell: imports Handler, delegates to api/routes.py, runs server.
 All business logic lives in api/*.
 """
+import logging
+import socket
+import sys
 import time
 import traceback
 from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 from urllib.parse import urlparse
 
+logger = logging.getLogger(__name__)
+
 from api.auth import check_auth
 from api.config import HOST, PORT, STATE_DIR, SESSION_DIR, DEFAULT_WORKSPACE
 from api.helpers import j
@@ -15,6 +20,28 @@ from api.routes import handle_get, handle_post
 from api.startup import auto_install_agent_deps, fix_credential_permissions
 
 
+class QuietHTTPServer(ThreadingHTTPServer):
+    """Custom HTTP server that silently handles common network errors."""
+    
+    def handle_error(self, request, client_address):
+        """Override to suppress logging for common client disconnect errors."""
+        exc_type, exc_value, _ = sys.exc_info()
+        
+        # Silently ignore common connection errors caused by client disconnects
+        if exc_type in (ConnectionResetError, BrokenPipeError, ConnectionAbortedError):
+            return
+        
+        # Also handle socket errors that indicate client disconnect
+        if exc_type is socket.error:
+            # errno 54 is Connection reset by peer on macOS/BSD
+            # errno 104 is Connection reset by peer on Linux
+            if exc_value.errno in (54, 104, 32):  # ECONNRESET, EPIPE
+                return
+        
+        # For other errors, use default logging
+        super().handle_error(request, client_address)
+
+
 class Handler(BaseHTTPRequestHandler):
     timeout = 30  # seconds — kills idle/incomplete connections to prevent thread exhaustion
     server_version = 'HermesWebUI/0.2'
@@ -118,7 +145,7 @@ def main() -> None:
     except Exception as e:
         print(f'[!!] WARNING: Gateway watcher failed to start: {e}', flush=True)
 
-    httpd = ThreadingHTTPServer((HOST, PORT), Handler)
+    httpd = QuietHTTPServer((HOST, PORT), Handler)
 
     # ── TLS/HTTPS setup (optional) ─────────────────────────────────────────
     from api.config import TLS_ENABLED, TLS_CERT, TLS_KEY
@@ -148,7 +175,7 @@ def main() -> None:
             from api.gateway_watcher import stop_watcher
             stop_watcher()
         except Exception:
-            pass
+            logger.debug("Failed to stop gateway watcher during shutdown")
 
 if __name__ == '__main__':
     main()