Add SQLite database module for persistent tracking

- Create aisbf/database.py with DatabaseManager class
- Track context dimensions (context_size, condense_context, condense_method, effective_context)
- Track token usage for rate limiting (TPM, TPH, TPD)
- Auto-create database at ~/.aisbf/aisbf.db if it doesn't exist
- Clean up old token usage records to prevent database bloat
- Export database module in __init__.py
- Update setup.py to include database.py in package data

aisbf/__init__.py

@@ -25,6 +25,7 @@ A modular proxy server for managing multiple AI provider integrations.
 
 from .config import config, Config, ProviderConfig, RotationConfig, AppConfig, AutoselectConfig, AutoselectModelInfo
 from .context import ContextManager, get_context_config_for_model
+from .database import DatabaseManager, get_database, initialize_database
 from .models import (
     Message,
     ChatCompletionRequest,

setup.py

@@ -96,6 +96,7 @@ setup(
             'aisbf/handlers.py',
             'aisbf/context.py',
             'aisbf/utils.py',
+            'aisbf/database.py',
         ]),
     ],
     entry_points={