Fix pydantic_settings import error

Added fallback implementation for environments without pydantic_settings package
and added pydantic-settings to requirements.txt to prevent future issues.

app/core/config.py

@@ -1,6 +1,33 @@
+import os
 from pathlib import Path
 
-from pydantic_settings import BaseSettings
+from pydantic import BaseModel
+
+# Try to use pydantic_settings if available, otherwise fallback to a simple BaseModel
+try:
+    from pydantic_settings import BaseSettings
+except ImportError:
+    # Fallback for environments without pydantic_settings
+    # In Pydantic v2, BaseSettings was moved to pydantic_settings package
+    class BaseSettings(BaseModel):
+        """
+        Simplified BaseSettings implementation for compatibility.
+        """
+        class Config:
+            env_file = ".env"
+            case_sensitive = True
+
+        def __init__(self, **kwargs):
+            # Load environment variables
+            env_values = {}
+            for field_name, _ in self.__annotations__.items():
+                env_val = os.environ.get(field_name)
+                if env_val is not None:
+                    env_values[field_name] = env_val
+            
+            # Override with any provided values
+            env_values.update(kwargs)
+            super().__init__(**env_values)
 
 
 class Settings(BaseSettings):

requirements.txt

@@ -3,6 +3,7 @@ uvicorn>=0.22.0
 sqlalchemy>=2.0.0
 alembic>=1.11.0
 pydantic>=2.0.0
+pydantic-settings>=2.0.0
 python-dotenv>=1.0.0
 ruff>=0.0.292
 pathlib>=1.0.1