refactor: integrate Alembic, restructure project, and clean up

- Add Alembic configuration (alembic.ini, env.py) for database migrations
- Remove legacy wheel.db and unnecessary __pycache__ files
- Delete models.py to separate SQLAlchemy and Pydantic concerns
- Restructure main.py to use modular API routers (user/admin)
- Introduce config backend for centralized settings management

backend/.config

@@ -0,0 +1,40 @@
+import sys
+from os.path import abspath, dirname
+import logging.config
+from alembic import context
+
+sys.path.insert(0, dirname(dirname(abspath(__file__))))
+
+from config import DATABASE_URL, LOGGING_CONFIG
+from database import Base, engine
+import models  
+
+#log-settings
+
+logging.config.dictConfig(LOGGING_CONFIG)
+
+target_metadata = Base.metadata
+
+def run_migrations_offline():
+    context.configure(
+        url=DATABASE_URL,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+def run_migrations_online():
+    with engine.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+        )
+        with context.begin_transaction():
+            context.run_migrations()
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()