feat: implement Instagram clone SocialPhoto API

- FastAPI backend with SQLite database
- JWT authentication (register, login)
- User profiles with follow/unfollow
- Posts with image upload and likes/dislikes
- Comments with likes
- Global and personalized feed
- Comprehensive pytest test suite (37 tests)

TASK-ID: 758f4029-702

tests/conftest.py

@@ -0,0 +1,129 @@
+"""Pytest fixtures for SocialPhoto tests."""
+import os
+import sqlite3
+from pathlib import Path
+from typing import Generator
+
+import pytest
+from fastapi.testclient import TestClient
+
+# Set test database path before importing app
+TEST_DB = Path(__file__).parent / "test_socialphoto.db"
+
+
+def override_db_path():
+    """Override database path for tests."""
+    return TEST_DB
+
+
+@pytest.fixture(scope="function")
+def db() -> Generator[sqlite3.Connection, None, None]:
+    """Create a fresh database for each test."""
+    # Remove existing test database
+    if TEST_DB.exists():
+        TEST_DB.unlink()
+
+    # Patch the database path before importing
+    import app.database as db_module
+    original_path = db_module.DATABASE_PATH
+    db_module.DATABASE_PATH = TEST_DB
+
+    # Initialize database with new path
+    db_module.init_db()
+
+    conn = db_module.get_db_connection()
+    conn.row_factory = sqlite3.Row
+
+    yield conn
+
+    conn.close()
+    db_module.DATABASE_PATH = original_path
+    if TEST_DB.exists():
+        TEST_DB.unlink()
+
+
+@pytest.fixture(scope="function")
+def client(db: sqlite3.Connection) -> Generator[TestClient, None, None]:
+    """Create a test client."""
+    from app.main import app
+    from app.database import get_db
+
+    # Override database dependency
+    def override_get_db():
+        yield db
+
+    app.dependency_overrides[get_db] = override_get_db
+
+    with TestClient(app) as test_client:
+        yield test_client
+
+    app.dependency_overrides.clear()
+
+
+def get_user_id_from_token(token: str) -> int:
+    """Extract user ID from JWT token (for test fixtures only)."""
+    from jose import jwt
+    from app.auth import SECRET_KEY, ALGORITHM
+    payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
+    return int(payload["sub"])
+
+
+@pytest.fixture
+def registered_user(client: TestClient) -> dict:
+    """Register a test user and return user data with token."""
+    response = client.post(
+        "/auth/register",
+        json={
+            "username": "testuser",
+            "email": "test@example.com",
+            "password": "testpass123",
+        },
+    )
+    assert response.status_code == 201
+    data = response.json()
+    token = data["access_token"]
+    user_id = get_user_id_from_token(token)
+    return {
+        "id": user_id,
+        "username": "testuser",
+        "email": "test@example.com",
+        "password": "testpass123",
+        "token": token,
+    }
+
+
+@pytest.fixture
+def two_users(client: TestClient) -> dict:
+    """Create two test users."""
+    # User 1
+    response = client.post(
+        "/auth/register",
+        json={
+            "username": "user1",
+            "email": "user1@example.com",
+            "password": "password123",
+        },
+    )
+    assert response.status_code == 201
+    token1 = response.json()["access_token"]
+
+    # User 2
+    response = client.post(
+        "/auth/register",
+        json={
+            "username": "user2",
+            "email": "user2@example.com",
+            "password": "password123",
+        },
+    )
+    assert response.status_code == 201
+    token2 = response.json()["access_token"]
+
+    return {
+        "user1_id": get_user_id_from_token(token1),
+        "user2_id": get_user_id_from_token(token2),
+        "user1_token": token1,
+        "user2_token": token2,
+        "user1_username": "user1",
+        "user2_username": "user2",
+    }