refactor(workspace): migrate from per-folder windows to single-window workspace

Replace the legacy folder + welcome routes with a unified /workspace route
that hosts all folders, conversations, tabs, and terminals in one window.

- Persist opened tabs to the database (opened_tabs entity + migration)
  so tab layout survives restarts and deep-link bootstrap restores state
- Replace FolderContext shim with AppWorkspaceProvider, ActiveFolderProvider,
  and TabProvider; expose both opened (folders) and full DB (allFolders)
  listings via list_all_folder_details
- Return conversations across all non-deleted folders from list_all when
  no folder filter is given, so the sidebar can show every folder's history
- Add ConversationContextBar above the chat input with folder picker
  (auto-opens unopened folders on select), branch picker, and commit /
  push / merge / stash entries to restore BranchDropdown functionality
- Rework sidebar with stats header, search, flat / folder-grouped view
  modes (localStorage-persisted), reveal-in-sidebar event subscriber,
  and per-folder context menu (focus, close tabs, remove from workspace);
  indent conversations under folder headers in grouped mode
- Gate terminal creation on active folder and show folder context
- Remove deprecated BranchDropdown, FolderNameDropdown, welcome route,
  and per-folder window commands
- Localize all new strings across 10 locales

src-tauri/src/web/router.rs

@@ -34,13 +34,21 @@ pub fn build_router(state: Arc<AppState>, token: String, static_dir: std::path::
             post(handlers::conversations::get_conversation),
         )
         .route(
-            "/list_folder_conversations",
-            post(handlers::conversations::list_folder_conversations),
+            "/list_all_conversations",
+            post(handlers::conversations::list_all_conversations),
         )
         .route(
             "/get_folder_conversation",
             post(handlers::conversations::get_folder_conversation),
         )
+        .route(
+            "/list_opened_tabs",
+            post(handlers::conversations::list_opened_tabs),
+        )
+        .route(
+            "/save_opened_tabs",
+            post(handlers::conversations::save_opened_tabs),
+        )
         .route(
             "/import_local_conversations",
             post(handlers::conversations::import_local_conversations),
@@ -81,13 +89,22 @@ pub fn build_router(state: Arc<AppState>, token: String, static_dir: std::path::
             post(handlers::folders::list_open_folders),
         )
         .route(
-            "/close_folder_window",
-            post(handlers::folders::close_folder_window),
+            "/list_open_folder_details",
+            post(handlers::folders::list_open_folder_details),
+        )
+        .route(
+            "/list_all_folder_details",
+            post(handlers::folders::list_all_folder_details),
         )
         .route("/get_folder", post(handlers::folders::get_folder))
+        .route("/open_folder", post(handlers::folders::open_folder))
         .route(
-            "/open_folder_window",
-            post(handlers::folders::open_folder_window),
+            "/open_folder_by_id",
+            post(handlers::folders::open_folder_by_id),
+        )
+        .route(
+            "/remove_folder_from_workspace",
+            post(handlers::folders::remove_folder_from_workspace),
         )
         .route(
             "/add_folder_to_history",
@@ -105,10 +122,6 @@ pub fn build_router(state: Arc<AppState>, token: String, static_dir: std::path::
             "/create_folder_directory",
             post(handlers::folders::create_folder_directory),
         )
-        .route(
-            "/save_folder_opened_conversations",
-            post(handlers::folders::save_folder_opened_conversations),
-        )
         .route("/get_git_branch", post(handlers::folders::get_git_branch))
         .route(
             "/get_home_directory",