Add distributed agent architecture for multi-node signal intelligence

Features:
- Standalone agent server (intercept_agent.py) for remote sensor nodes
- Controller API blueprint for agent management and data aggregation
- Push mechanism for agents to send data to controller
- Pull mechanism for controller to proxy requests to agents
- Multi-agent SSE stream for combined data view
- Agent management page at /controller/manage
- Agent selector dropdown in main UI
- GPS integration for location tagging
- API key authentication for secure agent communication
- Integration with Intercept's dependency checking system

New files:
- intercept_agent.py: Remote agent HTTP server
- intercept_agent.cfg: Agent configuration template
- routes/controller.py: Controller API endpoints
- utils/agent_client.py: HTTP client for agents
- utils/trilateration.py: Multi-agent position calculation
- static/js/core/agents.js: Frontend agent management
- templates/agents.html: Agent management page
- docs/DISTRIBUTED_AGENTS.md: System documentation

Modified:
- app.py: Register controller blueprint
- utils/database.py: Add agents and push_payloads tables
- templates/index.html: Add agent selector section

routes/__init__.py

@@ -21,6 +21,7 @@ def register_blueprints(app):
     from .listening_post import listening_post_bp
     from .tscm import tscm_bp, init_tscm_state
     from .spy_stations import spy_stations_bp
+    from .controller import controller_bp
 
     app.register_blueprint(pager_bp)
     app.register_blueprint(sensor_bp)
@@ -41,6 +42,7 @@ def register_blueprints(app):
     app.register_blueprint(listening_post_bp)
     app.register_blueprint(tscm_bp)
     app.register_blueprint(spy_stations_bp)
+    app.register_blueprint(controller_bp)  # Remote agent controller
 
     # Initialize TSCM state with queue and lock from app
     import app as app_module