Refactor and improve code consistency across multiple files

- Enhanced SQL queries in `session.go` and `share.go` for clarity and consistency.
- Updated comments for better understanding and maintenance.
- Ensured consistent error handling and return statements across various methods.

backend/internal/handlers/share.go

@@ -153,6 +153,7 @@ func (h *ShareHandler) DeleteShare(c *gin.Context) {
 
 	c.Status(204)
 }
+
 // CreateShareLink generates a public share link
 func (h *ShareHandler) CreateShareLink(c *gin.Context) {
 	documentID, err := uuid.Parse(c.Param("id"))
@@ -290,4 +291,4 @@ func (h *ShareHandler) RevokeShareLink(c *gin.Context) {
 
 	// c.JSON(http.StatusOK, gin.H{"message": "Share link revoked successfully"})
 	c.Status(204)
-}
+}