M2-T03: add read-only data JSON API

- GET /api/locations (inclusive time window start/end, pagination, cap 5000)
- GET /api/poo (pagination, cap 1000, newest first)
- GET /api/public-ip (current state + recent history, cap 1000)
- all session-protected, read-only, bounded (no full-table export)
- typed response schemas; register router; regenerate openapi/
- tests/test_api_data.py

app/schemas/data.py

@@ -0,0 +1,76 @@
+from __future__ import annotations
+
+from datetime import datetime
+
+from pydantic import BaseModel
+
+
+# ---------------------------------------------------------------------------
+# Location
+# ---------------------------------------------------------------------------
+
+
+class LocationRecord(BaseModel):
+    person: str
+    datetime: str
+    latitude: float
+    longitude: float
+    altitude: float | None
+
+
+class LocationsResponse(BaseModel):
+    items: list[LocationRecord]
+    limit: int
+    offset: int
+
+
+# ---------------------------------------------------------------------------
+# Poo
+# ---------------------------------------------------------------------------
+
+
+class PooRecord(BaseModel):
+    timestamp: str
+    status: str
+    latitude: float
+    longitude: float
+
+
+class PooResponse(BaseModel):
+    items: list[PooRecord]
+    limit: int
+    offset: int
+
+
+# ---------------------------------------------------------------------------
+# Public IP
+# ---------------------------------------------------------------------------
+
+
+class PublicIPStateSchema(BaseModel):
+    id: int
+    current_ipv4: str
+    previous_ipv4: str | None
+    first_seen_at: datetime
+    last_checked_at: datetime
+    last_changed_at: datetime | None
+    last_check_status: str
+    last_check_error: str | None
+    last_provider: str | None
+
+    model_config = {"from_attributes": True}
+
+
+class PublicIPHistorySchema(BaseModel):
+    id: int
+    ipv4: str
+    observed_at: datetime
+    change_type: str
+    provider: str | None
+
+    model_config = {"from_attributes": True}
+
+
+class PublicIPResponse(BaseModel):
+    state: PublicIPStateSchema | None
+    history: list[PublicIPHistorySchema]