Add user onboarding, keyboard overlay, and DB support

Introduce first-time user onboarding and a navigable on-screen keyboard, plus persistent user storage via a bundled rusqlite database and Tauri API. Backend: add rusqlite dependency, DB initialization in tauri setup, schema migration/backfill for users, and two Tauri commands (get_first_user, create_user) with input sanitization and structured UserRecord. Frontend: add core/users.js (invoke + localStorage fallback), integrate user state initialization, add user setup view/styles and keyboard overlay (JS/CSS), wire views and navigation to show onboarding when needed, and update lock view behavior to coordinate onboarding and passkey flow. Also add @tauri-apps/api dependency and update package/Cargo lock files accordingly.

package-lock.json

@@ -8,7 +8,8 @@
       "name": "nebula-os",
       "version": "0.1.0",
       "dependencies": {
-        "@nebulaproject/core": "^0.1.3"
+        "@nebulaproject/core": "^0.1.3",
+        "@tauri-apps/api": "^2.10.1"
       },
       "devDependencies": {
         "@tauri-apps/cli": "^2"
@@ -20,6 +21,16 @@
       "integrity": "sha512-sOjH10J1qSyqRNNi0yM3GAhkQk6lLGgmPPoyEljGfPC2Ty3iBoY44ML0sfepiiedVtedbkeDPpDcyx/UbVis6g==",
       "license": "MIT"
     },
+    "node_modules/@tauri-apps/api": {
+      "version": "2.10.1",
+      "resolved": "https://registry.npmjs.org/@tauri-apps/api/-/api-2.10.1.tgz",
+      "integrity": "sha512-hKL/jWf293UDSUN09rR69hrToyIXBb8CjGaWC7gfinvnQrBVvnLr08FeFi38gxtugAVyVcTa5/FD/Xnkb1siBw==",
+      "license": "Apache-2.0 OR MIT",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/tauri"
+      }
+    },
     "node_modules/@tauri-apps/cli": {
       "version": "2.10.0",
       "resolved": "https://registry.npmjs.org/@tauri-apps/cli/-/cli-2.10.0.tgz",