feat: add gunicorn + gevent production server via start.sh

Add start.sh as the recommended production entry point with:
- gunicorn + gevent worker for concurrent SSE/WebSocket handling
- CLI flags for port, host, debug, HTTPS, and dependency checks
- Auto-fallback to Flask dev server if gunicorn not installed
- Conditional gevent monkey-patch in app.py via INTERCEPT_USE_GEVENT env var
- Docker CMD updated to use start.sh
- Updated all docs, setup.sh, and requirements.txt accordingly

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/FEATURES.md

@@ -466,6 +466,7 @@ The settings modal shows availability status for each bundled asset:
 ## General
 
 - **Web-based interface** - no desktop app needed
+- **Production server** - gunicorn + gevent via `start.sh` for concurrent SSE/WebSocket handling (falls back to Flask dev server)
 - **Live message streaming** via Server-Sent Events (SSE)
 - **Audio alerts** with mute toggle
 - **Message export** to CSV/JSON

docs/HARDWARE.md

@@ -139,10 +139,13 @@ pip install -r requirements.txt
 After installation:
 
 ```bash
-sudo -E venv/bin/python intercept.py
+sudo ./start.sh
 
 # Custom port
-INTERCEPT_PORT=8080 sudo -E venv/bin/python intercept.py
+sudo ./start.sh -p 8080
+
+# HTTPS
+sudo ./start.sh --https
 ```
 
 Open **http://localhost:5050** in your browser.

docs/SECURITY.md

@@ -18,10 +18,9 @@ By default, INTERCEPT binds to `0.0.0.0:5050`, making it accessible from any net
    echo "block in on en0 proto tcp from any to any port 5050" | sudo pfctl -ef -
    ```
 
-2. **Bind to Localhost**: For local-only access, set the host environment variable:
+2. **Bind to Localhost**: For local-only access, set the host or use the CLI flag:
    ```bash
-   export INTERCEPT_HOST=127.0.0.1
-   python intercept.py
+   sudo ./start.sh -H 127.0.0.1
    ```
 
 3. **Trusted Networks Only**: Only run INTERCEPT on networks you trust. The application has no authentication mechanism.

docs/TROUBLESHOOTING.md

@@ -25,7 +25,7 @@ sudo apt install python3-flask python3-requests python3-serial python3-skyfield
 # Then create venv with system packages
 python3 -m venv --system-site-packages venv
 source venv/bin/activate
-sudo venv/bin/python intercept.py
+sudo ./start.sh
 ```
 
 ### "error: externally-managed-environment" (pip blocked)
@@ -61,7 +61,7 @@ sudo apt install python3.11 python3.11-venv python3-pip
 python3.11 -m venv venv
 source venv/bin/activate
 pip install -r requirements.txt
-sudo venv/bin/python intercept.py
+sudo ./start.sh
 ```
 
 ### Alternative: Use the setup script
@@ -336,7 +336,7 @@ rtl_fm -M am -f 118000000 -s 24000 -r 24000 -g 40 2>/dev/null | \
 
 Run INTERCEPT with sudo:
 ```bash
-sudo -E venv/bin/python intercept.py
+sudo ./start.sh
 ```
 
 ### Interface not found after enabling monitor mode

docs/USAGE.md

@@ -172,7 +172,7 @@ Set the following environment variables (Docker recommended):
 ```bash
 INTERCEPT_ADSB_AUTO_START=true \
 INTERCEPT_SHARED_OBSERVER_LOCATION=false \
-sudo -E venv/bin/python intercept.py
+sudo ./start.sh
 ```
 
 **Docker example (.env)**
@@ -518,10 +518,26 @@ INTERCEPT can be configured via environment variables:
 | `INTERCEPT_LOG_LEVEL` | `WARNING` | Log level (DEBUG, INFO, WARNING, ERROR) |
 | `INTERCEPT_DEFAULT_GAIN` | `40` | Default RTL-SDR gain |
 
-Example: `INTERCEPT_PORT=8080 sudo -E venv/bin/python intercept.py`
+Example: `INTERCEPT_PORT=8080 sudo ./start.sh`
 
 ## Command-line Options
 
+### Production server (recommended)
+
+```
+./start.sh --help
+
+  -p, --port PORT    Port to listen on (default: 5050)
+  -H, --host HOST    Host to bind to (default: 0.0.0.0)
+  -d, --debug        Run in debug mode (Flask dev server)
+  --https            Enable HTTPS with self-signed certificate
+  --check-deps       Check dependencies and exit
+```
+
+`start.sh` auto-detects gunicorn + gevent and runs a production WSGI server with cooperative greenlets — this handles multiple SSE streams and WebSocket connections concurrently without blocking. Falls back to the Flask dev server if gunicorn is not installed.
+
+### Development server
+
 ```
 python3 intercept.py --help
 

docs/index.html

@@ -331,7 +331,7 @@
                         <pre><code>git clone https://github.com/smittix/intercept.git
 cd intercept
 ./setup.sh
-sudo -E venv/bin/python intercept.py</code></pre>
+sudo ./start.sh</code></pre>
                     </div>
                     <p class="install-note">Requires Python 3.9+ and RTL-SDR drivers</p>
                 </div>