fix: Update Pydantic v2 configuration for .env loading

- Fix ConfigDict model_config for Pydantic v2.12+ compatibility
- Add env_file and env_file_encoding to all config classes
- Each config class now properly loads from .env with correct prefix

Fixes: ValidationError when loading settings from .env file
CLI now works correctly with 'uv run python main.py'

config.py

@@ -1,11 +1,19 @@
 """Configuration management using Pydantic settings."""
 from pydantic_settings import BaseSettings
+from pydantic import ConfigDict
 from typing import Optional
 import os
 
 
-class DatabaseConfig(BaseSettings):
-    """Database configuration."""
+class MySQLConfig(BaseSettings):
+    """MySQL source database configuration."""
+    model_config = ConfigDict(
+        env_prefix="MYSQL_",
+        case_sensitive=False,
+        extra="ignore",
+        env_file=".env",
+        env_file_encoding="utf-8"
+    )
 
     host: str
     port: int
@@ -13,60 +21,66 @@ class DatabaseConfig(BaseSettings):
     password: str
     database: str
 
-    class Config:
-        env_prefix: str = ""
 
-
-class MySQLConfig(DatabaseConfig):
-    """MySQL source database configuration."""
-
-    class Config:
-        env_prefix: str = "MYSQL_"
-
-
-class PostgreSQLConfig(DatabaseConfig):
+class PostgreSQLConfig(BaseSettings):
     """PostgreSQL target database configuration."""
+    model_config = ConfigDict(
+        env_prefix="POSTGRES_",
+        case_sensitive=False,
+        extra="ignore",
+        env_file=".env",
+        env_file_encoding="utf-8"
+    )
 
-    class Config:
-        env_prefix: str = "POSTGRES_"
+    host: str
+    port: int
+    user: str
+    password: str
+    database: str
 
 
 class MigrationSettings(BaseSettings):
     """Migration settings."""
+    model_config = ConfigDict(
+        case_sensitive=False,
+        extra="ignore",
+        env_file=".env",
+        env_file_encoding="utf-8"
+    )
 
     batch_size: int = 10000
     log_level: str = "INFO"
     dry_run: bool = False
 
-    class Config:
-        env_file = ".env"
-        case_sensitive = False
-
 
 class BenchmarkSettings(BaseSettings):
     """Benchmark settings."""
+    model_config = ConfigDict(
+        env_prefix="BENCHMARK_",
+        case_sensitive=False,
+        extra="ignore",
+        env_file=".env",
+        env_file_encoding="utf-8"
+    )
 
     output_dir: str = "benchmark_results"
     iterations: int = 5
 
-    class Config:
-        env_prefix: str = "BENCHMARK_"
-        env_file = ".env"
-        case_sensitive = False
-
 
 class Settings(BaseSettings):
     """All application settings."""
+    model_config = ConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+        extra="ignore"
+    )
 
     mysql: MySQLConfig
     postgres: PostgreSQLConfig
     migration: MigrationSettings
     benchmark: BenchmarkSettings
 
-    class Config:
-        env_file = ".env"
-        case_sensitive = False
-
     @classmethod
     def from_env(cls):
         """Load settings from environment variables."""