feat: camera batch endpoint implementation and tests

Self-contained server stub and pytest tests for the /api/v1/camera/events/batch
endpoint, mirroring the BLE batch pattern with idempotent INSERT on
(device_id, period_start).

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

server/test_camera_endpoint.py

@@ -0,0 +1,91 @@
+# server/test_camera_endpoint.py
+# Template tests for the camera batch endpoint.
+# Adapt imports and fixtures to match the actual server's test structure.
+#
+# To run against the actual server (once integrated):
+#   pytest server/test_camera_endpoint.py -v
+
+import json
+import sqlite3
+
+import pytest
+
+# These imports will need to match the actual server module structure:
+# from main import app, get_db, verify_device_hmac
+# from fastapi.testclient import TestClient
+
+
+def make_camera_batch_body(location_id: str, period_start: int,
+                            period_end: int, entries: int, exits: int) -> str:
+    return json.dumps({
+        "location_id": location_id,
+        "records": [{
+            "period_start": period_start,
+            "period_end": period_end,
+            "entries": entries,
+            "exits": exits,
+        }]
+    })
+
+
+def _make_db() -> sqlite3.Connection:
+    db = sqlite3.connect(":memory:")
+    db.execute("""
+        CREATE TABLE camera_records (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            device_id TEXT NOT NULL,
+            location_id TEXT NOT NULL,
+            period_start INTEGER NOT NULL,
+            period_end INTEGER NOT NULL,
+            entries INTEGER NOT NULL,
+            exits INTEGER NOT NULL,
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE(device_id, period_start)
+        )
+    """)
+    db.commit()
+    return db
+
+
+def test_insert_logic_idempotent():
+    """Unit test for the insert logic — no FastAPI needed."""
+    db = _make_db()
+
+    from server.camera_endpoint import CameraRecord, CameraEventsRequest, receive_camera_events_impl
+
+    batch = CameraEventsRequest(
+        location_id="test-loc",
+        records=[CameraRecord(period_start=1712000000, period_end=1712003600,
+                               entries=5, exits=3)]
+    )
+
+    resp1 = receive_camera_events_impl(batch, "dc-test-01", db)
+    assert resp1.status == "ok"
+    assert resp1.accepted == 1
+
+    # Second identical call — idempotent
+    resp2 = receive_camera_events_impl(batch, "dc-test-01", db)
+    assert resp2.status == "ok"
+    assert resp2.accepted == 0
+
+
+def test_entries_exits_stored_correctly():
+    """Verify entries and exits are stored as submitted."""
+    db = _make_db()
+
+    from server.camera_endpoint import CameraRecord, CameraEventsRequest, receive_camera_events_impl
+
+    batch = CameraEventsRequest(
+        location_id="retailer-123",
+        records=[CameraRecord(period_start=1712007200, period_end=1712010800,
+                               entries=42, exits=39)]
+    )
+    receive_camera_events_impl(batch, "dc-0042", db)
+
+    row = db.execute(
+        "SELECT entries, exits, location_id FROM camera_records WHERE device_id=?",
+        ("dc-0042",)
+    ).fetchone()
+    assert row[0] == 42
+    assert row[1] == 39
+    assert row[2] == "retailer-123"