feat: add Termux/Android prerequisite detection

Detects when running in Termux on Android and checks for required
prerequisites before starting the server:
- Termux:API package installed
- Location services enabled and accessible
- Wake lock available

Exits with informative error message if prerequisites not met.
Adds `rf-mapper check-termux` command for manual verification.

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

src/rf_mapper/__main__.py

@@ -169,6 +169,9 @@ Note: Requires sudo for WiFi/Bluetooth scanning.
     web_parser.add_argument('--profile-requests', action='store_true', help='Enable profiling')
     web_parser.add_argument('--log-requests', action='store_true', help='Log requests')
 
+    # Check-termux command
+    subparsers.add_parser('check-termux', help='Check Termux/Android prerequisites')
+
     # Config command
     config_parser = subparsers.add_parser('config', help='Show/edit configuration')
     config_parser.add_argument(
@@ -209,6 +212,8 @@ Note: Requires sudo for WiFi/Bluetooth scanning.
             run_status(data_dir)
         elif args.command == 'config':
             run_config(args, config)
+        elif args.command == 'check-termux':
+            run_check_termux()
         elif args.command == 'web':
             run_web_deprecated(args, config, data_dir)
         else:
@@ -436,6 +441,19 @@ Home Assistant:
     """)
 
 
+def run_check_termux():
+    """Check Termux/Android prerequisites"""
+    from .termux import is_termux, check_termux_prerequisites
+
+    if not is_termux():
+        print("Not running in Termux/Android environment.")
+        print("This check is only relevant when running on Android via Termux.")
+        sys.exit(0)
+
+    success = check_termux_prerequisites(verbose=True)
+    sys.exit(0 if success else 1)
+
+
 def get_pid_file(data_dir: Path) -> Path:
     """Get path to PID file"""
     return data_dir / "rf-mapper.pid"
@@ -534,6 +552,16 @@ def run_start(args, config: Config, data_dir: Path):
     import subprocess
     import time
 
+    # Check Termux prerequisites if running on Android
+    from .termux import is_termux, check_termux_prerequisites, setup_termux_signal_handlers
+
+    if is_termux():
+        if not check_termux_prerequisites(verbose=True):
+            print("Exiting due to missing prerequisites.")
+            sys.exit(1)
+        # Set up signal handlers for graceful shutdown
+        setup_termux_signal_handlers()
+
     host = args.host or config.web.host
     port = args.port or config.web.port
     debug = getattr(args, 'debug', False)