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

app/database.py

@@ -0,0 +1,120 @@
+"""Database module for SocialPhoto."""
+import sqlite3
+from pathlib import Path
+from typing import Optional
+
+DATABASE_PATH = Path(__file__).parent.parent / "socialphoto.db"
+
+
+def get_db_connection() -> sqlite3.Connection:
+    """Get a database connection with row factory."""
+    conn = sqlite3.connect(DATABASE_PATH, check_same_thread=False)
+    conn.row_factory = sqlite3.Row
+    return conn
+
+
+def get_db() -> sqlite3.Connection:
+    """Dependency for FastAPI routes."""
+    conn = get_db_connection()
+    try:
+        yield conn
+    finally:
+        conn.close()
+
+
+def init_db() -> None:
+    """Initialize the database with all tables."""
+    conn = get_db_connection()
+    cursor = conn.cursor()
+
+    # Users table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS users (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            username TEXT UNIQUE NOT NULL,
+            email TEXT UNIQUE NOT NULL,
+            password_hash TEXT NOT NULL,
+            avatar_url TEXT DEFAULT '/static/default-avatar.png',
+            bio TEXT DEFAULT '',
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+        )
+    """)
+
+    # Posts table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS posts (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            user_id INTEGER NOT NULL REFERENCES users(id),
+            image_path TEXT NOT NULL,
+            caption TEXT DEFAULT '',
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+        )
+    """)
+
+    # Comments table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS comments (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            post_id INTEGER NOT NULL REFERENCES posts(id),
+            user_id INTEGER NOT NULL REFERENCES users(id),
+            content TEXT NOT NULL,
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+        )
+    """)
+
+    # Likes table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS likes (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            post_id INTEGER NOT NULL REFERENCES posts(id),
+            user_id INTEGER NOT NULL REFERENCES users(id),
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE(post_id, user_id)
+        )
+    """)
+
+    # Dislikes table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS dislikes (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            post_id INTEGER NOT NULL REFERENCES posts(id),
+            user_id INTEGER NOT NULL REFERENCES users(id),
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE(post_id, user_id)
+        )
+    """)
+
+    # Follows table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS follows (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            follower_id INTEGER NOT NULL REFERENCES users(id),
+            following_id INTEGER NOT NULL REFERENCES users(id),
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE(follower_id, following_id)
+        )
+    """)
+
+    # Comment likes table
+    cursor.execute("""
+        CREATE TABLE IF NOT EXISTS comment_likes (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            comment_id INTEGER NOT NULL REFERENCES comments(id),
+            user_id INTEGER NOT NULL REFERENCES users(id),
+            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+            UNIQUE(comment_id, user_id)
+        )
+    """)
+
+    conn.commit()
+    conn.close()
+
+
+def row_to_dict(row: sqlite3.Row) -> dict:
+    """Convert a sqlite Row to a dictionary."""
+    return dict(row)
+
+
+if __name__ == "__main__":
+    init_db()
+    print("Database initialized successfully.")