feat: initial CamWatch service

Polls Frigate events API, extracts dominant vehicle color (KMeans),
reads LPR plate from Frigate sub_label. Responsive dark UI with
filter by plate/camera/date and auto-refresh. FastAPI + SQLite.

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

app/database.py

@@ -0,0 +1,101 @@
+import sqlite3
+import os
+
+DB_PATH = os.environ.get("DB_PATH", "/data/camwatch.db")
+
+def get_db():
+    conn = sqlite3.connect(DB_PATH)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+def init_db():
+    conn = get_db()
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS events (
+            id TEXT PRIMARY KEY,
+            camera TEXT,
+            start_time INTEGER,
+            snapshot_path TEXT,
+            plate TEXT,
+            color_hex TEXT,
+            color_name TEXT,
+            processed_at INTEGER
+        )
+    """)
+    conn.commit()
+    conn.close()
+
+def event_exists(event_id: str) -> bool:
+    conn = get_db()
+    row = conn.execute("SELECT id FROM events WHERE id = ?", (event_id,)).fetchone()
+    conn.close()
+    return row is not None
+
+def insert_event(event_id, camera, start_time, snapshot_path, plate, color_hex, color_name):
+    import time
+    conn = get_db()
+    conn.execute("""
+        INSERT OR IGNORE INTO events
+        (id, camera, start_time, snapshot_path, plate, color_hex, color_name, processed_at)
+        VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+    """, (event_id, camera, start_time, snapshot_path, plate, color_hex, color_name, int(time.time())))
+    conn.commit()
+    conn.close()
+
+def get_events(limit=100, offset=0, plate_filter=None, camera_filter=None, date_filter=None):
+    conn = get_db()
+    query = "SELECT * FROM events WHERE 1=1"
+    params = []
+    if plate_filter:
+        query += " AND plate LIKE ?"
+        params.append(f"%{plate_filter}%")
+    if camera_filter:
+        query += " AND camera = ?"
+        params.append(camera_filter)
+    if date_filter:
+        import time
+        from datetime import datetime
+        try:
+            dt = datetime.strptime(date_filter, "%Y-%m-%d")
+            ts_start = int(dt.timestamp())
+            ts_end = ts_start + 86400
+            query += " AND start_time >= ? AND start_time < ?"
+            params.extend([ts_start, ts_end])
+        except Exception:
+            pass
+    query += " ORDER BY start_time DESC LIMIT ? OFFSET ?"
+    params.extend([limit, offset])
+    rows = conn.execute(query, params).fetchall()
+    conn.close()
+    return [dict(r) for r in rows]
+
+def count_events(plate_filter=None, camera_filter=None, date_filter=None):
+    conn = get_db()
+    query = "SELECT COUNT(*) FROM events WHERE 1=1"
+    params = []
+    if plate_filter:
+        query += " AND plate LIKE ?"
+        params.append(f"%{plate_filter}%")
+    if camera_filter:
+        query += " AND camera = ?"
+        params.append(camera_filter)
+    if date_filter:
+        import time
+        from datetime import datetime
+        try:
+            dt = datetime.strptime(date_filter, "%Y-%m-%d")
+            ts_start = int(dt.timestamp())
+            ts_end = ts_start + 86400
+            query += " AND start_time >= ? AND start_time < ?"
+            params.extend([ts_start, ts_end])
+        except Exception:
+            pass
+    count = conn.execute(query, params).fetchone()[0]
+    conn.close()
+    return count
+
+def get_cameras():
+    conn = get_db()
+    rows = conn.execute("SELECT DISTINCT camera FROM events ORDER BY camera").fetchall()
+    conn.close()
+    return [r[0] for r in rows]