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

.gitignore

@@ -10,17 +10,17 @@ venv/
 ENV/
 uv.lock
 
-# Logs
-*.log
-pager_messages.log
-
-# Local data
-downloads/
-pgdata/
-
-# Local data
-downloads/
-pgdata/
+# Logs
+*.log
+pager_messages.log
+
+# Local data
+downloads/
+pgdata/
+
+# Local data
+downloads/
+pgdata/
 
 # IDE
 .idea/
@@ -42,4 +42,15 @@ build/
 uv.lock
 *.db
 *.sqlite3
-intercept.db
+intercept.db
+
+# Instance folder (contains database with user data)
+instance/
+
+# Agent configs with real credentials (keep template only)
+intercept_agent_*.cfg
+!intercept_agent.cfg
+
+# Temporary files
+/tmp/
+*.tmp