Refactor database access to use a unified dbAdapter for SQLite and PostgreSQL

- Replaced direct database calls with dbAdapter methods in fieldRoutes, itemRoutes, listRoutes, syncRoutes, and webRoutes.
- Implemented a new db.ts file to handle database interactions for both SQLite and PostgreSQL.
- Added WebSocket support for real-time synchronization in WebSocketSyncClient and ws.ts.
- Updated TypeScript configuration to include WebSocket types.
- Created a new WebSocket server for handling sync requests and responses.
- Ensured compatibility with both SQLite and PostgreSQL by using parameterized queries.

CollabTableServer/.env.example

@@ -1,4 +1,35 @@
+#################################################################
+# Server
+#################################################################
 PORT=3000
-DB_PATH=/data/collabtable.db
 NODE_ENV=production
 SERVER_PASSWORD=your_secure_password_here
+
+#################################################################
+# Database backend selection
+# - sqlite  (default if not set)
+# - postgres
+#################################################################
+# Choose the DB client; if omitted or not set to "postgres", SQLite is used
+DB_CLIENT=sqlite
+
+#################################################################
+# SQLite configuration (used when DB_CLIENT=sqlite)
+#################################################################
+# Path to the SQLite database file. Default in code: ./data/collabtable.db
+# For Docker, you may prefer a volume path like /data/collabtable.db
+DB_PATH=/data/collabtable.db
+
+#################################################################
+# PostgreSQL configuration (used when DB_CLIENT=postgres)
+# You can either provide a single DATABASE_URL or the PG* variables below
+#################################################################
+# Example URL: postgres://user:password@localhost:5432/collabtable
+DATABASE_URL=
+
+# If DATABASE_URL is not set, these individual settings are used:
+PGHOST=localhost
+PGPORT=5432
+PGUSER=postgres
+PGPASSWORD=
+PGDATABASE=collabtable