fix: modernize pydantic config to remove deprecation warning

- Replace deprecated class Config pattern with model_config = ConfigDict(...)
- Add ConfigDict import from pydantic
- Fixes PydanticDeprecatedSince20 warning in test output
- Maintains all existing functionality

All 73 tests pass without warnings.

steward/config.py

@@ -13,7 +13,7 @@ import os
 from pathlib import Path
 
 from omegaconf import OmegaConf
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, ConfigDict, Field
 
 logger = logging.getLogger(__name__)
 
@@ -68,17 +68,14 @@ class ToolsConfig(BaseModel):
 class Settings(BaseModel):
     """Application settings with OmegaConf and pydantic integration."""
 
+    model_config = ConfigDict(arbitrary_types_allowed=True)
+
     telegram: TelegramConfig = Field(default_factory=TelegramConfig)
     openai: OpenAIConfig = Field(default_factory=OpenAIConfig)
     analysis: AnalysisConfig = Field(default_factory=AnalysisConfig)
     memory: MemoryConfig = Field(default_factory=MemoryConfig)
     tools: ToolsConfig = Field(default_factory=ToolsConfig)
 
-    class Config:
-        """Pydantic config."""
-
-        arbitrary_types_allowed = True
-
     # Compatibility properties for existing code
     @property
     def telegram_bot_token(self) -> str: