Add skip tracking, compressed heatmap, listening log, docs, tests, and OpenAI support

Major changes:
- Add skip tracking: poll currently-playing every 15s, detect skips (<30s listened)
- Add listening-log and sessions API endpoints
- Fix ReccoBeats client to extract spotify_id from href response
- Compress heatmap from 24 hours to 6 x 4-hour blocks
- Add OpenAI support in narrative service (use max_completion_tokens for new models)
- Add ListeningLog component with timeline and list views
- Update all frontend components to use real data (album art, play counts)
- Add docker-compose external network (dockernet) support
- Add comprehensive documentation (API, DATA_MODEL, ARCHITECTURE, FRONTEND)
- Add unit tests for ingest and API endpoints

backend/tests/test_main.py

@@ -0,0 +1,49 @@
+import pytest
+from unittest.mock import MagicMock, patch, AsyncMock
+from datetime import datetime
+
+
+@pytest.fixture
+def mock_db():
+    return MagicMock()
+
+
+class TestSnapshotsEndpoint:
+    def test_snapshots_endpoint_exists(self, mock_db):
+        with patch("app.main.SessionLocal", return_value=mock_db):
+            from fastapi.testclient import TestClient
+            from app.main import app
+
+            mock_db.query.return_value.order_by.return_value.limit.return_value.all.return_value = []
+
+            with TestClient(app) as client:
+                response = client.get("/snapshots?limit=1")
+                assert response.status_code == 200
+
+
+class TestListeningLogEndpoint:
+    def test_listening_log_endpoint_exists(self, mock_db):
+        with patch("app.main.SessionLocal", return_value=mock_db):
+            from fastapi.testclient import TestClient
+            from app.main import app
+
+            mock_db.query.return_value.options.return_value.filter.return_value.order_by.return_value.limit.return_value.all.return_value = []
+
+            with TestClient(app) as client:
+                response = client.get("/listening-log?days=7&limit=100")
+                assert response.status_code == 200
+
+
+class TestSessionsEndpoint:
+    def test_sessions_endpoint_exists(self, mock_db):
+        with patch("app.main.SessionLocal", return_value=mock_db):
+            from fastapi.testclient import TestClient
+            from app.main import app
+
+            mock_db.query.return_value.options.return_value.filter.return_value.order_by.return_value.all.return_value = []
+
+            with TestClient(app) as client:
+                response = client.get("/sessions?days=7")
+                assert response.status_code == 200
+                data = response.json()
+                assert "session_list" in data