TASK-001: Setup FastAPI project structure

- Fixed main.py to include all route routers (posts, users, comments, feed)
- Renamed app/models.py to app/schemas.py and split into proper schema modules
- Fixed schema imports in routes
- Updated app/models/__init__.py to properly export SQLAlchemy models
- Fixed database imports in route files
- App imports and runs correctly

app/schemas/user.py

@@ -0,0 +1,20 @@
+"""User schemas for SocialPhoto API."""
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, ConfigDict
+
+
+class UserBase(BaseModel):
+    """Base user model."""
+    username: str
+    email: str
+    avatar_url: Optional[str] = "/static/default-avatar.png"
+    bio: Optional[str] = ""
+
+
+class UserStats(BaseModel):
+    """User statistics model."""
+    posts_count: int
+    followers_count: int
+    following_count: int