desktop M10.4: Rust local SQLite store + Tauri commands

The on-device core that makes the desktop app work with no server and no login.

- rusqlite (bundled SQLite, so no system libsqlite dependency to vary across
  builds); uuid v4 ids; RFC3339/Date.toISOString-compatible timestamps.
- Schema mirroring the note model: notes, labels, note_labels (with via_tag),
  checklist_items, attachments, link_previews, note_revisions, saved_filters,
  plus per-row sync_revision/dirty + a sync_state row for the M10.7 engine.
  user_version-gated migrations.
- derive.rs: pure [[wiki-link]] + #tag scanners (mirror the frontend inline
  rules, no regex dep) with unit tests; #tags re-sync via_tag labels on save,
  [[links]] drive backlinks at query time (derived, never stored).
- store.rs: the full repository surface (facet/label/date/text list, create,
  PATCH-semantics update, pin/archive/color/kind, checklist items, labels CRUD
  + merge, reminders complete/snooze, reorder, trash/restore/delete, revisions
  + restore, titles/search/backlinks/link-search, saved filters).
- commands.rs: ~38 #[tauri::command]s over a Mutex<Connection> in managed state.
- lib.rs: opens the DB in the platform app-data dir on setup; synthetic offline
  config/user so the auth-gated router resolves with no login.

Attachment upload / URL unfurl / import are intentionally deferred (network/file
concerns); adapters/local.ts (M10.5) wires all of the above via invoke.

Task 1993.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

desktop/src-tauri/src/lib.rs

@@ -7,6 +7,7 @@
 //! AppImage) and boots the UI.
 
 mod integration;
+mod local;
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
@@ -14,10 +15,56 @@ pub fn run() {
     harden_linux_webkit_rendering();
 
     tauri::Builder::default()
+        .setup(|app| {
+            use tauri::Manager;
+            // The on-device store lives in the platform app-data dir (e.g. Linux
+            // ~/.local/share/com.fabledsword.thoughtsync/thoughtsync.db), created on
+            // first launch. This is what makes the app work with no server or login.
+            let dir = app.path().app_data_dir()?;
+            std::fs::create_dir_all(&dir)?;
+            app.manage(local::open(&dir.join("thoughtsync.db"))?);
+            Ok(())
+        })
         .invoke_handler(tauri::generate_handler![
             integration::integration_status,
             integration::integrate_desktop,
             integration::unintegrate_desktop,
+            local::commands::config_get,
+            local::commands::auth_me,
+            local::commands::notes_list,
+            local::commands::notes_get,
+            local::commands::notes_create,
+            local::commands::notes_create_titled,
+            local::commands::notes_update,
+            local::commands::notes_complete_reminder,
+            local::commands::notes_snooze_reminder,
+            local::commands::notes_set_labels,
+            local::commands::notes_add_item,
+            local::commands::notes_update_item,
+            local::commands::notes_delete_item,
+            local::commands::notes_delete_attachment,
+            local::commands::notes_delete_preview,
+            local::commands::notes_reorder,
+            local::commands::notes_trash,
+            local::commands::notes_restore,
+            local::commands::notes_delete_forever,
+            local::commands::notes_revisions,
+            local::commands::notes_restore_revision,
+            local::commands::notes_reminders,
+            local::commands::notes_titles,
+            local::commands::notes_search,
+            local::commands::notes_backlinks,
+            local::commands::notes_link_search,
+            local::commands::labels_list,
+            local::commands::labels_create,
+            local::commands::labels_rename,
+            local::commands::labels_set_color,
+            local::commands::labels_remove,
+            local::commands::labels_merge,
+            local::commands::saved_filters_list,
+            local::commands::saved_filters_create,
+            local::commands::saved_filters_remove,
+            local::commands::saved_filters_rename,
         ])
         .run(tauri::generate_context!())
         .expect("error while running the ThoughtSync desktop app");