Major security and code quality improvements

Security:
- Add input validation for all API endpoints (frequency, lat/lon, device, gain, ppm)
- Add HTML escaping utility to prevent XSS attacks
- Add path traversal protection for log file configuration
- Add proper HTTP status codes for error responses (400, 409, 503)

Performance:
- Reduce SSE keepalive overhead (30s interval instead of 1s)
- Add centralized SSE stream utility with optimized keepalive
- Add DataStore class for thread-safe data with automatic cleanup

New Features:
- Add data export endpoints (/export/aircraft, /export/wifi, /export/bluetooth)
- Support for both JSON and CSV export formats
- Add process cleanup on application exit (atexit handlers)
- Label Iridium module as demo mode with clear warnings

Code Quality:
- Create utils/validation.py for centralized input validation
- Create utils/sse.py for SSE stream utilities
- Create utils/cleanup.py for memory management
- Add safe_terminate() and register_process() for process management
- Improve error handling with proper logging throughout routes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

routes/bluetooth.py

@@ -19,6 +19,8 @@ from flask import Blueprint, jsonify, request, Response
 
 import app as app_module
 from utils.dependencies import check_tool
+from utils.logging import bluetooth_logger as logger
+from utils.sse import format_sse
 from data.oui import OUI_DATABASE, load_oui_database, get_manufacturer
 from data.patterns import AIRTAG_PREFIXES, TILE_PREFIXES, SAMSUNG_TRACKER
 
@@ -469,12 +471,19 @@ def get_bt_devices():
 def stream_bt():
     """SSE stream for Bluetooth events."""
     def generate():
+        last_keepalive = time.time()
+        keepalive_interval = 30.0
+
         while True:
             try:
                 msg = app_module.bt_queue.get(timeout=1)
-                yield f"data: {json.dumps(msg)}\n\n"
+                last_keepalive = time.time()
+                yield format_sse(msg)
             except queue.Empty:
-                yield f"data: {json.dumps({'type': 'keepalive'})}\n\n"
+                now = time.time()
+                if now - last_keepalive >= keepalive_interval:
+                    yield format_sse({'type': 'keepalive'})
+                    last_keepalive = now
 
     response = Response(generate(), mimetype='text/event-stream')
     response.headers['Cache-Control'] = 'no-cache'