feat(sidebar): reorder folder groups by drag and persist sort order

src-tauri/src/db/migration/m20260422_000001_folder_sort_order.rs

@@ -0,0 +1,72 @@
+use sea_orm_migration::prelude::*;
+use sea_orm_migration::sea_orm::{ConnectionTrait, DbBackend, Statement};
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .alter_table(
+                Table::alter()
+                    .table(Folder::Table)
+                    .add_column(
+                        ColumnDef::new(Folder::SortOrder)
+                            .integer()
+                            .not_null()
+                            .default(0),
+                    )
+                    .to_owned(),
+            )
+            .await?;
+
+        // Backfill sort_order by current last_opened_at DESC so existing users
+        // see the same order after migration. We use a correlated subquery that
+        // works on SQLite without ROW_NUMBER/window functions.
+        let conn = manager.get_connection();
+        let sql = "UPDATE folder SET sort_order = (\
+            SELECT COUNT(*) FROM folder AS inner_f \
+            WHERE inner_f.last_opened_at > folder.last_opened_at \
+               OR (inner_f.last_opened_at = folder.last_opened_at AND inner_f.id < folder.id) \
+        ) + 1";
+        conn.execute(Statement::from_string(DbBackend::Sqlite, sql.to_string()))
+            .await?;
+
+        manager
+            .create_index(
+                Index::create()
+                    .name("idx_folder_sort_order")
+                    .table(Folder::Table)
+                    .col(Folder::SortOrder)
+                    .to_owned(),
+            )
+            .await
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .drop_index(
+                Index::drop()
+                    .name("idx_folder_sort_order")
+                    .table(Folder::Table)
+                    .to_owned(),
+            )
+            .await?;
+
+        manager
+            .alter_table(
+                Table::alter()
+                    .table(Folder::Table)
+                    .drop_column(Folder::SortOrder)
+                    .to_owned(),
+            )
+            .await
+    }
+}
+
+#[derive(DeriveIden)]
+enum Folder {
+    Table,
+    SortOrder,
+}

src-tauri/src/db/migration/mod.rs

@@ -10,6 +10,7 @@ mod m20260401_000001_chat_channel_sender_context;
 mod m20260404_000001_model_provider;
 mod m20260406_000001_agent_setting_model_provider;
 mod m20260420_000001_opened_tabs;
+mod m20260422_000001_folder_sort_order;
 pub struct Migrator;
 
 #[async_trait::async_trait]
@@ -26,6 +27,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260404_000001_model_provider::Migration),
             Box::new(m20260406_000001_agent_setting_model_provider::Migration),
             Box::new(m20260420_000001_opened_tabs::Migration),
+            Box::new(m20260422_000001_folder_sort_order::Migration),
         ]
     }
 }