Add isolated Gemini image proxy

gemini_proxy/test_app.py

@@ -0,0 +1,31 @@
+from fastapi.testclient import TestClient
+
+from app import app
+
+
+def test_health() -> None:
+    client = TestClient(app)
+    response = client.get("/health")
+    assert response.status_code == 200
+    assert response.json() == {"status": "ok"}
+
+
+def test_rejects_unsupported_type() -> None:
+    client = TestClient(app)
+    response = client.post(
+        "/gemini",
+        files={"image": ("input.txt", b"not-an-image", "text/plain")},
+        data={"prompt": "test", "generation_config": "{}"},
+    )
+    assert response.status_code == 415
+
+
+def test_missing_key_returns_service_unavailable(monkeypatch) -> None:
+    monkeypatch.delenv("GEMINI_API_KEY", raising=False)
+    client = TestClient(app)
+    response = client.post(
+        "/gemini",
+        files={"image": ("input.png", b"not-an-image", "image/png")},
+        data={"prompt": "test", "generation_config": "{}"},
+    )
+    assert response.status_code == 503