feat: implement periodic session cleanup for inactive/orphaned sessions

Implements automatic cleanup of Signal sessions to prevent database growth:

**Configuration (environment variables):**
- BAILEYS_SESSION_CLEANUP_ENABLED=true (default: true)
- BAILEYS_SESSION_CLEANUP_INTERVAL=86400000 (24h default)
- BAILEYS_SESSION_CLEANUP_HOUR=3 (3am default)
- BAILEYS_SESSION_SECONDARY_INACTIVE_DAYS=15
- BAILEYS_SESSION_PRIMARY_INACTIVE_DAYS=30
- BAILEYS_SESSION_LID_ORPHAN_HOURS=24

**Cleanup rules:**
1. Secondary devices (Web, Desktop): inactive > 15 days
2. Primary devices: inactive > 30 days
3. LID orphans (no PN mapping): > 24 hours

**Safety guarantees:**
- Does NOT affect WebSocket connections
- Does NOT cause message loss (Signal Protocol auto-recreates sessions)
- Runs in low-traffic hours (3am default, configurable)
- Atomic transactions (all-or-nothing)
- Comprehensive logging and statistics

**Implementation:**
- src/Signal/session-cleanup.ts: Core cleanup logic
- src/Defaults/index.ts: Configuration defaults
- src/Socket/socket.ts: Integration and lifecycle management

**Note:** Activity tracking not yet implemented (required for time-based cleanup).
Current implementation only cleans LID orphans (sessions without PN mapping).

https://claude.ai/code/session_01SoNUGBEWbJwWWws3F2fuzh

src/Defaults/index.ts

@@ -194,6 +194,27 @@ export const DEFAULT_CACHE_MAX_KEYS = {
 	LID_GLOBAL: 10_000
 }
 
+/**
+ * Session cleanup configuration - removes inactive/orphaned Signal sessions
+ * Prevents unbounded database growth while maintaining security
+ *
+ * Environment variables:
+ * - BAILEYS_SESSION_CLEANUP_ENABLED: Enable/disable cleanup (default: true)
+ * - BAILEYS_SESSION_CLEANUP_INTERVAL: Cleanup interval in ms (default: 24h)
+ * - BAILEYS_SESSION_CLEANUP_HOUR: Hour to run cleanup (default: 3 = 3am)
+ * - BAILEYS_SESSION_SECONDARY_INACTIVE_DAYS: Days before cleaning secondary devices (default: 15)
+ * - BAILEYS_SESSION_PRIMARY_INACTIVE_DAYS: Days before cleaning primary device (default: 30)
+ * - BAILEYS_SESSION_LID_ORPHAN_HOURS: Hours before cleaning orphaned LID sessions (default: 24)
+ */
+export const DEFAULT_SESSION_CLEANUP_CONFIG = {
+	enabled: process.env.BAILEYS_SESSION_CLEANUP_ENABLED !== 'false',
+	intervalMs: parseInt(process.env.BAILEYS_SESSION_CLEANUP_INTERVAL || '86400000', 10), // 24h
+	cleanupHour: parseInt(process.env.BAILEYS_SESSION_CLEANUP_HOUR || '3', 10), // 3am
+	secondaryDeviceInactiveDays: parseInt(process.env.BAILEYS_SESSION_SECONDARY_INACTIVE_DAYS || '15', 10),
+	primaryDeviceInactiveDays: parseInt(process.env.BAILEYS_SESSION_PRIMARY_INACTIVE_DAYS || '30', 10),
+	lidOrphanHours: parseInt(process.env.BAILEYS_SESSION_LID_ORPHAN_HOURS || '24', 10)
+}
+
 // Re-export retry constants for backwards compatibility
 // Actual definitions are in retry-utils.ts to avoid ESM initialization order issues
 export { RETRY_BACKOFF_DELAYS, RETRY_JITTER_FACTOR } from '../Utils/retry-utils'