Refactor into modular structure with improvements

- Split monolithic intercept.py (15k lines) into modular structure:
  - routes/ - Flask blueprints for each feature
  - templates/ - Jinja2 HTML templates
  - data/ - OUI database, satellite TLEs, detection patterns
  - utils/ - dependencies, process management, logging
  - config.py - centralized configuration with env var support

- Add type hints to function signatures
- Replace bare except clauses with specific exceptions
- Add proper logging module (replaces print statements)
- Add environment variable support (INTERCEPT_* prefix)
- Add test suite with pytest
- Add Dockerfile for containerized deployment
- Add pyproject.toml with ruff/black/mypy config
- Add requirements-dev.txt for development dependencies

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

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

utils/process.py

@@ -0,0 +1,80 @@
+from __future__ import annotations
+
+import subprocess
+import re
+from typing import Any
+
+from .dependencies import check_tool
+
+
+def cleanup_stale_processes() -> None:
+    """Kill any stale processes from previous runs (but not system services)."""
+    # Note: dump1090 is NOT included here as users may run it as a system service
+    processes_to_kill = ['rtl_adsb', 'rtl_433', 'multimon-ng', 'rtl_fm']
+    for proc_name in processes_to_kill:
+        try:
+            subprocess.run(['pkill', '-9', proc_name], capture_output=True)
+        except (subprocess.SubprocessError, OSError):
+            pass
+
+
+def is_valid_mac(mac: str | None) -> bool:
+    """Validate MAC address format."""
+    if not mac:
+        return False
+    return bool(re.match(r'^([0-9A-Fa-f]{2}:){5}[0-9A-Fa-f]{2}$', mac))
+
+
+def is_valid_channel(channel: str | int | None) -> bool:
+    """Validate WiFi channel number."""
+    try:
+        ch = int(channel)  # type: ignore[arg-type]
+        return 1 <= ch <= 200
+    except (ValueError, TypeError):
+        return False
+
+
+def detect_devices() -> list[dict[str, Any]]:
+    """Detect RTL-SDR devices."""
+    devices: list[dict[str, Any]] = []
+
+    if not check_tool('rtl_test'):
+        return devices
+
+    try:
+        result = subprocess.run(
+            ['rtl_test', '-t'],
+            capture_output=True,
+            text=True,
+            timeout=5
+        )
+        output = result.stderr + result.stdout
+
+        # Parse device info
+        device_pattern = r'(\d+):\s+(.+?)(?:,\s*SN:\s*(\S+))?$'
+
+        for line in output.split('\n'):
+            line = line.strip()
+            match = re.match(device_pattern, line)
+            if match:
+                devices.append({
+                    'index': int(match.group(1)),
+                    'name': match.group(2).strip().rstrip(','),
+                    'serial': match.group(3) or 'N/A'
+                })
+
+        if not devices:
+            found_match = re.search(r'Found (\d+) device', output)
+            if found_match:
+                count = int(found_match.group(1))
+                for i in range(count):
+                    devices.append({
+                        'index': i,
+                        'name': f'RTL-SDR Device {i}',
+                        'serial': 'Unknown'
+                    })
+
+    except Exception:
+        pass
+
+    return devices