security: Fix 10 vulnerabilities, remove 12 dead code instances

Critical fixes:
- Remove hardcoded admin/admin123 credentials from UserManager
- Enable JWT signature verification (was disabled for debugging)
- Redact secrets from /dev/config endpoint (was exposing os.environ)
- Remove hardcoded SSH admin/admin credentials from hardware service
- Add channel validation to prevent command injection in router interface

Rust fixes:
- Replace partial_cmp().unwrap() with .unwrap_or(Equal) to prevent
  NaN panics in 6 locations across core, signal, nn, mat crates
- Replace .expect()/.unwrap() with safe fallbacks in utils, csi_receiver
- Replace SystemTime unwrap with unwrap_or_default

Dead code removed:
- Duplicate imports (CORSMiddleware, os, Path, ABC, subprocess)
- Unused AdaptiveRateLimit/RateLimitStorage/RedisRateLimitStorage (~110 lines)
- Unused _log_authentication_event method
- Unused Confidence::new_unchecked in Rust
- Fix bare except: clause to except Exception:

https://claude.ai/code/session_01Ki7pvEZtJDvqJkmyn6B714

v1/src/tasks/backup.py

@@ -8,11 +8,9 @@ import os
 import shutil
 import gzip
 import json
-import subprocess
 from datetime import datetime, timedelta
 from pathlib import Path
 from typing import Dict, Any, Optional, List
-from contextlib import asynccontextmanager
 
 from sqlalchemy import select, text
 from sqlalchemy.ext.asyncio import AsyncSession

v1/src/tasks/monitoring.py

@@ -8,9 +8,8 @@ import psutil
 import time
 from datetime import datetime, timedelta
 from typing import Dict, Any, Optional, List
-from contextlib import asynccontextmanager
 
-from sqlalchemy import select, func, and_, or_
+from sqlalchemy import select, func
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.config.settings import Settings