Add Dangerous Pi MVP implementation - complete backend and system integration

This commit adds the complete Dangerous Pi web management interface with all MVP features implemented and tested locally.

## New Features

### Backend (Python + FastAPI)
- Complete FastAPI backend with async support
- 40+ API endpoints (Health, PM3, WiFi, Updates, UPS, BLE, Plugins)
- 6 managers: Session, WiFi, Update, UPS, BLE, Plugin
- SQLite database with sessions, config, history, crash reports
- Server-Sent Events (SSE) for real-time notifications
- Mock PM3 worker for development without hardware

### WiFi Manager
- Interface detection (USB vs built-in)
- Network scanning with signal strength
- Mode switching (AP/Client/Dual/Auto/Off)
- Network connection with password support
- Hidden SSID and saved networks support
- Static IP and DHCP configuration
- 10 WiFi API endpoints

### Update Manager
- GitHub releases API integration
- Automatic periodic update checks
- Semantic version comparison
- Update download with progress tracking
- SHA256 checksum verification
- Automatic installation with backup and rollback
- PM3 client rebuild after updates
- 6 Update API endpoints

### UPS Manager
- I2C battery monitoring (MAX17040-compatible)
- Battery percentage, voltage, current tracking
- Power source detection (AC/Battery)
- Safe shutdown triggers at configurable thresholds
- Event callbacks for battery warnings
- SSE and BLE notification integration
- 3 UPS API endpoints

### BLE Manager
- Bluetooth Low Energy notification support
- Auto-detects BLE capability
- Multiple notification types (updates, battery, shutdown, etc.)
- BLE advertising management
- Device connection tracking
- 4 BLE API endpoints

### Plugin Framework
- Dynamic plugin loading/unloading
- Plugin lifecycle management (load, enable, disable, unload)
- Hook system for extensibility
- JSON-based metadata
- Example "Hello World" plugin included
- 7 Plugin API endpoints

### Frontend (Remix.js + React)
- Cyberpunk-themed responsive UI
- Dashboard with system status
- PM3 command interface with history
- Settings page with WiFi and Update management
- Command logs viewer
- Theme toggle (Dark/Light/Auto)
- Server-side rendering (SSR)
- Mobile-first responsive design

### System Integration
- Systemd service with security hardening
- Automated install/uninstall scripts
- Environment configuration template
- Hardware access groups (i2c, bluetooth, gpio, dialout)
- Pi-gen stage 04 integration for OS image building
- Port conflict resolution with ttyd-bash
- I2C interface auto-enable for UPS HAT

### Testing
- test_backend.py - Backend API tests
- test_ups.py - UPS manager tests
- test_ble.py - BLE manager tests
- test_plugins.py - Plugin manager tests
- All tests passing locally

### Documentation
- 12 comprehensive documentation files
- claude.md - AI development guide
- WIFI_MANAGER.md - WiFi management guide
- UPDATE_MANAGER.md - Update system guide
- PORT_CONFLICT.md - Port conflict resolution guide
- MVP_COMPLETE.md - MVP implementation summary
- PROJECT_STATUS.md - Project status and roadmap
- systemd/README.md - Service management docs
- pi-gen integration documentation

## Technical Details
- ~5,000+ lines of backend code
- 11 Python dependencies (smbus2 added for UPS)
- FastAPI with async/await throughout
- Type hints and docstrings on all functions
- RESTful API design with SSE for notifications
- Security hardening (non-root, protected dirs, resource limits)

## Next Steps
- Deploy to Raspberry Pi Zero 2 W hardware
- Test with real Proxmark3 device
- Test UPS HAT integration
- Test BLE on Pi hardware
- Build custom OS image with pi-gen
- Performance optimization for Pi Zero 2 W

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

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

app/backend/config.py

@@ -0,0 +1,44 @@
+"""Configuration settings for Dangerous Pi backend."""
+import os
+from pathlib import Path
+
+# Base paths
+BASE_DIR = Path(__file__).parent.parent.parent
+DATA_DIR = BASE_DIR / "data"
+LOGS_DIR = BASE_DIR / "logs"
+
+# Database
+DATABASE_PATH = DATA_DIR / "dangerous_pi.db"
+
+# Proxmark3 settings
+PM3_DEVICE = os.getenv("PM3_DEVICE", "/dev/ttyACM0")
+PM3_TIMEOUT = int(os.getenv("PM3_TIMEOUT", "30"))
+
+# Session settings
+SESSION_TIMEOUT = int(os.getenv("SESSION_TIMEOUT", "300"))  # 5 minutes
+MAX_SESSIONS = 1
+
+# Server settings
+HOST = os.getenv("HOST", "0.0.0.0")
+PORT = int(os.getenv("PORT", "8000"))
+VERSION = os.getenv("VERSION", "0.1.0")
+
+# Update settings
+GITHUB_REPO = os.getenv("GITHUB_REPO", "yourusername/dangerous-pi")  # TODO: Update this
+UPDATE_CHECK_INTERVAL = int(os.getenv("UPDATE_CHECK_INTERVAL", "3600"))  # 1 hour
+
+# Wi-Fi settings
+WLAN_INTERFACE = os.getenv("WLAN_INTERFACE", "wlan0")
+USB_WLAN_INTERFACE = os.getenv("USB_WLAN_INTERFACE", "wlan1")
+
+# UPS settings
+UPS_I2C_ADDRESS = os.getenv("UPS_I2C_ADDRESS", "0x36")
+UPS_CHECK_INTERVAL = int(os.getenv("UPS_CHECK_INTERVAL", "60"))  # 1 minute
+
+# BLE settings
+BLE_ENABLED = os.getenv("BLE_ENABLED", "true").lower() == "true"
+BLE_DEVICE_NAME = os.getenv("BLE_DEVICE_NAME", "DangerousPi")
+
+# Security
+AUTH_ENABLED = os.getenv("AUTH_ENABLED", "false").lower() == "true"
+HTTPS_ENABLED = os.getenv("HTTPS_ENABLED", "false").lower() == "true"