feat: Initial project scaffold

Flask API backend for ESP32 sensor fleet:
- App factory pattern with blueprints
- SQLAlchemy 2.x models (Sensor, Device, Sighting, Alert, Event, Probe)
- UDP collector for sensor data streams
- REST API endpoints for sensors, devices, alerts, events, probes, stats
- pytest setup with fixtures
- Containerfile for podman deployment
- Makefile for common tasks

README.md

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+# ESP32-Web
+
+REST API backend for ESP32 sensor fleet (OPSEC/OSINT/Purple team).
+
+## Quick Start
+
+```bash
+# Install
+pip install -e ".[dev]"
+
+# Initialize database
+flask --app src/esp32_web db init
+flask --app src/esp32_web db migrate -m "initial"
+flask --app src/esp32_web db upgrade
+
+# Run development server
+make dev
+```
+
+## Ports
+
+| Port | Protocol | Description |
+|------|----------|-------------|
+| 5500 | TCP | HTTP REST API |
+| 5500 | UDP | Sensor data collector |
+| 5501 | UDP | Sensor commands (outbound) |
+
+## API Endpoints
+
+| Method | Endpoint | Description |
+|--------|----------|-------------|
+| GET | `/health` | Health check |
+| GET | `/api/v1/sensors` | List sensors |
+| GET | `/api/v1/sensors/<hostname>` | Get sensor |
+| POST | `/api/v1/sensors/<hostname>/command` | Send command |
+| GET | `/api/v1/devices` | List devices |
+| GET | `/api/v1/devices/<mac>` | Get device |
+| GET | `/api/v1/alerts` | List alerts |
+| GET | `/api/v1/events` | List events |
+| GET | `/api/v1/probes` | List probe requests |
+| GET | `/api/v1/probes/ssids` | List SSIDs |
+| GET | `/api/v1/stats` | Statistics |
+
+## Container
+
+```bash
+make build
+make run
+make logs
+make stop
+```
+
+## Testing
+
+```bash
+make test
+```