Phase 4: Implement REST API component

- Add FastAPI application with lifespan management
- Implement bearer token authentication (read/admin levels)
- Create comprehensive REST API routes:
  - Nodes: list, get by public key
  - Node tags: CRUD operations
  - Messages: list with filters, get by ID
  - Advertisements: list with filters, get by ID
  - Telemetry: list with filters, get by ID
  - Trace paths: list with filters, get by ID
  - Commands: send message, channel message, advertisement
  - Dashboard: stats API and HTML dashboard
- Add API CLI command for running the server
- Create API test suite with 44 passing tests

Routes use proper RESTful status codes (201 Created, 204 No Content).
Authentication is optional - when keys not configured, endpoints are open.

tests/test_api/test_trace_paths.py

@@ -0,0 +1,42 @@
+"""Tests for trace path API routes."""
+
+import pytest
+
+
+class TestListTracePaths:
+    """Tests for GET /trace-paths endpoint."""
+
+    def test_list_trace_paths_empty(self, client_no_auth):
+        """Test listing trace paths when database is empty."""
+        response = client_no_auth.get("/api/v1/trace-paths")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["items"] == []
+        assert data["total"] == 0
+
+    def test_list_trace_paths_with_data(self, client_no_auth, sample_trace_path):
+        """Test listing trace paths with data in database."""
+        response = client_no_auth.get("/api/v1/trace-paths")
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data["items"]) == 1
+        assert data["total"] == 1
+        assert data["items"][0]["path_hashes"] == sample_trace_path.path_hashes
+        assert data["items"][0]["hop_count"] == sample_trace_path.hop_count
+
+
+class TestGetTracePath:
+    """Tests for GET /trace-paths/{id} endpoint."""
+
+    def test_get_trace_path_success(self, client_no_auth, sample_trace_path):
+        """Test getting a specific trace path."""
+        response = client_no_auth.get(f"/api/v1/trace-paths/{sample_trace_path.id}")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["id"] == sample_trace_path.id
+        assert data["path_hashes"] == sample_trace_path.path_hashes
+
+    def test_get_trace_path_not_found(self, client_no_auth):
+        """Test getting a non-existent trace path."""
+        response = client_no_auth.get("/api/v1/trace-paths/nonexistent-id")
+        assert response.status_code == 404