Fix MongoDB DateTime serialization issues - Replace chrono::DateTime with mongodb::bson::DateTime in models - Update API responses to use timestamp_millis() for JSON serialization - Fix User, Share model DateTime fields - Update all handler responses to return i64 timestamps - This fixes the Kind: invalid type: map, expected RFC 3339 error

backend/src/handlers/users.rs

@@ -20,8 +20,8 @@ pub struct UserProfileResponse {
     pub id: String,
     pub email: String,
     pub username: String,
-    pub created_at: String,
-    pub last_active: String,
+    pub created_at: i64,
+    pub last_active: i64,
     pub email_verified: bool,
 }
 
@@ -33,8 +33,8 @@ impl TryFrom<User> for UserProfileResponse {
             id: user.id.map(|id| id.to_string()).unwrap_or_default(),
             email: user.email,
             username: user.username,
-            created_at: user.created_at.to_rfc3339(),
-            last_active: user.last_active.to_rfc3339(),
+            created_at: user.created_at.timestamp_millis(),
+            last_active: user.last_active.timestamp_millis(),
             email_verified: user.email_verified,
         })
     }