refactor(database): unify database connections and add retry logic

Refactor LocalDataSource to reuse the shared database connection from database.ts, avoiding OPFS file handle conflicts. Add retry logic with exponential backoff for database open operations, particularly important for Web/OPFS environments. Also add dynamic theme support to chat input and message bubble styles, using theme colors instead of hardcoded values for better light/dark mode support.

BREAKING CHANGE: Database initialization now requires userId to be passed explicitly for user-specific databases

tsconfig.json

@@ -2,9 +2,8 @@
   "extends": "expo/tsconfig.base",
   "compilerOptions": {
     "strict": true,
-    "baseUrl": ".",
     "paths": {
-      "@/*": ["src/*"]
+      "@/*": ["./src/*"]
     },
     "skipLibCheck": true,
     "moduleResolution": "bundler",