fixes unbounded memory caches that could lead to oom issues. Document-level caches would accumulate indefinitely as users edited files.

replaced all DashMap usages with appropriate data structures based on access patterns:
Bounded Memory Caches (LRU):

• PgQueryStore: DashMap → Mutex<LruCache<1000>> - AST parsing cache
• TreeSitterStore: DashMap → Mutex<LruCache<1000>> - CST parsing cache
• AnnotationStore: DashMap → Mutex<LruCache<1000>> - Statement annotations cache

Read-Heavy Workloads (RwLock):

• SchemaCacheManager: DashMap → RwLock - Database schema cache
• ConnectionManager: DashMap → RwLock - Database connection pool cache
• WorkspaceServer.documents: DashMap → RwLock - Open document cache