feat(logging): implement configurable belief state logging

- Add LoggingConfig model and logging field to GlobalSettings
- Implement belief_scope context manager for structured logging
- Add configure_logger for dynamic level and file rotation settings
- Add logging configuration UI to Settings page
- Update ConfigManager to apply logging settings on initialization and updates

backend/src/core/config_manager.py

@@ -16,7 +16,7 @@ import os
 from pathlib import Path
 from typing import Optional, List
 from .config_models import AppConfig, Environment, GlobalSettings
-from .logger import logger
+from .logger import logger, configure_logger
 # [/SECTION]
 
 # [DEF:ConfigManager:Class]
@@ -38,10 +38,13 @@ class ConfigManager:
         # 2. Logic implementation
         self.config_path = Path(config_path)
         self.config: AppConfig = self._load_config()
-        
+
+        # Configure logger with loaded settings
+        configure_logger(self.config.settings.logging)
+
         # 3. Runtime check of @POST
         assert isinstance(self.config, AppConfig), "self.config must be an instance of AppConfig"
-        
+
         logger.info(f"[ConfigManager][Exit] Initialized")
     # [/DEF:__init__]
 
@@ -120,7 +123,10 @@ class ConfigManager:
         # 2. Logic implementation
         self.config.settings = settings
         self.save()
-        
+
+        # Reconfigure logger with new settings
+        configure_logger(settings.logging)
+
         logger.info(f"[update_global_settings][Exit] Settings updated")
     # [/DEF:update_global_settings]