feat: Enhance real-time collaboration features with user awareness and document sharing

- Added user information (UserID, UserName, UserAvatar) to Client struct for presence tracking.
- Implemented failure handling in the broadcastMessage function to manage send failures and disconnect clients if necessary.
- Introduced document ownership and sharing capabilities:
  - Added OwnerID and Is_Public fields to Document model.
  - Created DocumentShare model for managing document sharing with permissions.
  - Implemented functions for creating, listing, and managing document shares in the Postgres store.
- Added user management functionality:
  - Created User model and associated functions for user management in the Postgres store.
  - Implemented session management with token hashing for security.
- Updated database schema with migrations for users, sessions, and document shares.
- Enhanced frontend Yjs integration with awareness event logging for user connections and disconnections.

backend/go.mod

@@ -3,25 +3,31 @@ module github.com/M1ngdaXie/realtime-collab
 go 1.25.3
 
 require (
+	github.com/gin-contrib/cors v1.7.6
+	github.com/gin-gonic/gin v1.11.0
+	github.com/golang-jwt/jwt/v5 v5.3.0
+	github.com/google/uuid v1.6.0
+	github.com/gorilla/websocket v1.5.3
+	github.com/joho/godotenv v1.5.1
+	github.com/lib/pq v1.10.9
+	golang.org/x/oauth2 v0.34.0
+)
+
+require (
+	cloud.google.com/go/compute/metadata v0.3.0 // indirect
 	github.com/bytedance/sonic v1.14.0 // indirect
 	github.com/bytedance/sonic/loader v0.3.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
 	github.com/gabriel-vasile/mimetype v1.4.9 // indirect
-	github.com/gin-contrib/cors v1.7.6 // indirect
 	github.com/gin-contrib/sse v1.1.0 // indirect
-	github.com/gin-gonic/gin v1.11.0 // indirect
 	github.com/go-playground/locales v0.14.1 // indirect
 	github.com/go-playground/universal-translator v0.18.1 // indirect
 	github.com/go-playground/validator/v10 v10.27.0 // indirect
 	github.com/goccy/go-json v0.10.5 // indirect
 	github.com/goccy/go-yaml v1.18.0 // indirect
-	github.com/google/uuid v1.6.0 // indirect
-	github.com/gorilla/websocket v1.5.3 // indirect
-	github.com/joho/godotenv v1.5.1 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect
 	github.com/leodido/go-urn v1.4.0 // indirect
-	github.com/lib/pq v1.10.9 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect