Add DB API endpoints: summary, history, date, camera, location

- api/db/summary — overall totals
- api/db/history — per-date rows
- api/db/date/<date> — single date detail with per-camera breakdown
- api/db/camera/<id> — all runs for a specific camera
- api/db/location/<name> — per-location summary + history
- API.md — full endpoint documentation with schema

API.md

@@ -0,0 +1,149 @@
+# Chicken Counter API
+
+Base URL: `http://<jetson-ip>:8080`
+
+## Live Dashboard
+
+### `GET /`
+Returns the dashboard HTML page.
+
+### `GET /api/cameras`
+List cameras currently writing to `/dev/shm`.
+
+```json
+{"cameras": ["CC1", "CC2", "CC3"]}
+```
+
+### `GET /shm/<camera_id>/stats.json`
+Live stats for the active pipeline.
+
+```json
+{
+  "frame_index": 5120,
+  "inside_box_count": 42,
+  "total_entered_count": 1858,
+  "track_count": 99,
+  "backward_active": false,
+  "smoothed_speed": 4.3,
+  "count_events": 0,
+  "run_date": "2026-06-10"
+}
+```
+
+### `GET /shm/<camera_id>/frame.jpg`
+Live JPEG frame from the active pipeline.
+
+---
+
+## Database
+
+All endpoints require the dashboard to be started with `--db <path>`. If no DB exists, endpoints return `[]` or `{}`.
+
+### `GET /api/db/summary`
+Overall totals across all dates and locations.
+
+```json
+{
+  "days": 12,
+  "locations": 2,
+  "total_runs": 48,
+  "total_chickens": 125000,
+  "total_hours": 8.5
+}
+```
+
+### `GET /api/db/history`
+Per-date summary, newest first (max 50 rows).
+
+```json
+[
+  {
+    "date": "2026-06-10",
+    "location": "kandang-atas",
+    "cams": 4,
+    "total": 5570,
+    "minutes": 40.2
+  }
+]
+```
+
+### `GET /api/db/date/<date>`
+Detail for a specific date. Format: `YYYY-MM-DD`.
+
+```json
+{
+  "date": "2026-06-10",
+  "total": {"total": 5570, "minutes": 40.2},
+  "cameras": [
+    {
+      "camera_id": "CC1",
+      "total_entered": 1500,
+      "frames_processed": 24800,
+      "elapsed_seconds": 600.5,
+      "stopped_reason": "backward",
+      "source_video": "kandang_1_camera_1_2026-06-10_120056.mp4",
+      "location": "kandang-atas"
+    }
+  ]
+}
+```
+
+### `GET /api/db/camera/<camera_id>`
+History for a specific camera across all dates (max 50 rows).
+
+```json
+[
+  {
+    "date": "2026-06-10",
+    "location": "kandang-atas",
+    "total_entered": 1500,
+    "frames_processed": 24800,
+    "elapsed_seconds": 600.5,
+    "stopped_reason": "backward"
+  }
+]
+```
+
+### `GET /api/db/location/<location>`
+Summary and history for a specific location.
+
+```json
+{
+  "location": "kandang-atas",
+  "summary": {"days": 5, "total": 25000, "hours": 3.2},
+  "history": [
+    {
+      "date": "2026-06-10",
+      "cameras": "CC1, CC2, CC3, CC4",
+      "total": 5570,
+      "minutes": 40.2
+    }
+  ]
+}
+```
+
+---
+
+## Database Schema
+
+```sql
+CREATE TABLE batch_runs (
+    id               INTEGER PRIMARY KEY AUTOINCREMENT,
+    date             TEXT    NOT NULL,
+    location         TEXT    NOT NULL,
+    camera_id        TEXT    NOT NULL,
+    total_entered    INTEGER NOT NULL DEFAULT 0,
+    frames_processed INTEGER NOT NULL DEFAULT 0,
+    elapsed_seconds  REAL    NOT NULL DEFAULT 0.0,
+    stopped_reason   TEXT    NOT NULL DEFAULT '',
+    source_video     TEXT    NOT NULL DEFAULT '',
+    generated_at     TEXT    NOT NULL DEFAULT '',
+    UNIQUE(date, location, camera_id)
+);
+```
+
+Data is inserted automatically by the batch runner when `location` and `db_path` are configured in the batch YAML, or manually via:
+
+```bash
+python3 store_results.py output/counts_2026-06-10.json --location kandang-atas --db chicken_counts.db
+```