feat(high): Fix memory leak in session management with SessionManager

Implemented comprehensive session lifecycle management:
- SessionManager class with LRU eviction policy
- Automatic cleanup of expired sessions
- Connection pooling and reuse
- Memory leak prevention

Features:
- LRU cache with configurable max_sessions limit
- Automatic eviction of least recently used sessions
- TTL-based session expiration (default: 1 hour)
- Background cleanup task (default: 5 minutes interval)
- Thread-safe session access with asyncio.Lock
- Statistics tracking (cache hits, misses, evictions)

Session Lifecycle:
1. get_session() - Get or create session (lazy initialization)
2. Session pooling - Reuse existing sessions
3. LRU eviction - Remove oldest when at capacity
4. TTL expiration - Cleanup inactive sessions
5. Graceful shutdown - Close all sessions on shutdown

Memory Leak Prevention:
- Proper connection cleanup via clear_session()
- Automatic eviction prevents unbounded growth
- Background task removes expired sessions
- Shutdown closes all active sessions

Integration:
- Added to DIContainer with lazy initialization
- Integrated into initialize() and shutdown() lifecycle
- Configurable via ErniConfig.data_dir

Configuration:
- max_sessions: 100 (prevents memory exhaustion)
- session_ttl: 3600 seconds (1 hour)
- cleanup_interval: 300 seconds (5 minutes)
- db_path: data/sessions.db (persistent storage)

Benefits:
- Prevents memory leaks from unclosed connections
- Reduces database connection overhead
- Improves performance with session reuse
- Automatic cleanup of stale sessions
- Thread-safe concurrent access

Tests:
- 13 comprehensive unit tests
- Test LRU eviction, TTL expiration, cleanup
- Test concurrent access, statistics
- All tests passing (13/13)

Before:
- Sessions created but never cleaned up
- Database connections left open
- Memory usage grows unbounded
- No session reuse

After:
- Automatic session lifecycle management
- Proper connection cleanup
- Bounded memory usage (max 100 sessions)
- Session pooling and reuse
- Background cleanup task

Resolves: openai#11 (HIGH priority)
Impact: Eliminates memory leaks and improves stability

Author: User

examples/erni-foto-agency/erni_foto_agency/di_container.py

@@ -27,6 +27,7 @@
 from .performance.circuit_breaker import CircuitBreaker
 from .performance.cost_optimizer import CostBudget, CostOptimizer
 from .performance.rate_limiter import RateLimiter, get_rate_limiter
+from .session.session_manager import SessionManager
 from .utils.image_processor import ImageProcessor
 
 logger = structlog.get_logger(__name__)
@@ -123,6 +124,7 @@ def __init__(self, config: ErniConfig | None = None):
         self._cost_optimizer: CostOptimizer | None = None
         self._rate_limiter_gpt4o: RateLimiter | None = None
         self._rate_limiter_gpt4o_mini: RateLimiter | None = None
+        self._session_manager: SessionManager | None = None
 
         # Agents (lazy-initialized)
         self._schema_extractor: SharePointSchemaExtractorAgent | None = None
@@ -274,6 +276,24 @@ def rate_limiter_gpt4o_mini(self, value: RateLimiter) -> None:
         """Set rate limiter for GPT-4o-mini (for testing)"""
         self._rate_limiter_gpt4o_mini = value
 
+    @property
+    def session_manager(self) -> SessionManager:
+        """Get session manager"""
+        if self._session_manager is None:
+            self._session_manager = SessionManager(
+                db_path=self._config.data_dir / "sessions.db",
+                max_sessions=100,
+                session_ttl=3600,  # 1 hour
+                cleanup_interval=300  # 5 minutes
+            )
+            logger.debug("Session manager created")
+        return self._session_manager
+
+    @session_manager.setter
+    def session_manager(self, value: SessionManager) -> None:
+        """Set session manager (for testing)"""
+        self._session_manager = value
+
     # ========================================================================
     # AI Agents
     # ========================================================================
@@ -371,6 +391,9 @@ async def initialize(self) -> None:
         # Initialize metrics collector
         await self.metrics_collector.start_background_tasks()
 
+        # Start session manager
+        await self.session_manager.start()
+
         self._initialized = True
         logger.info("DI Container initialized successfully")
 
@@ -387,6 +410,10 @@ async def shutdown(self) -> None:
 
         logger.info("Shutting down DI Container components...")
 
+        # Stop session manager
+        if self._session_manager:
+            await self._session_manager.shutdown()
+
         # Stop metrics collector (if it has stop method)
         if self._metrics_collector:
             if hasattr(self._metrics_collector, 'stop_background_tasks'):
@@ -419,6 +446,7 @@ def reset(self) -> None:
         self._cost_optimizer = None
         self._rate_limiter_gpt4o = None
         self._rate_limiter_gpt4o_mini = None
+        self._session_manager = None
         self._schema_extractor = None
         self._vision_analyzer = None
         self._sharepoint_uploader = None

examples/erni-foto-agency/erni_foto_agency/session/__init__.py

@@ -0,0 +1,6 @@
+"""Session management module"""
+
+from .session_manager import SessionManager, SessionMetadata
+
+__all__ = ["SessionManager", "SessionMetadata"]
+