feat(desktop): signature updater Tauri + wizard persistant + protocole E2E (#77)

- Signature des mises a jour Tauri : paire de cles minisign generee, cle publique dans tauri.conf.json, createUpdaterArtifacts actif, secrets CI exposes (repli build non signe si secret absent).

- Wizard 1er lancement : etat persistant wizard_done cote Rust (get_wizard_state/complete_wizard) pour ne plus reafficher la banniere, retro-compatible.

- Protocole des 6 tests E2E manuels : docs/DESKTOP_E2E_CHECKLIST.md.

- CI : desktop.test.mjs ajoute au job lint.

- Docs : ROADMAP, fiche desktop-tauri, CHANGELOG, README desktop, guide releases.

- fix(build): retirer les libs WeasyPrint inutiles du stage builder Docker.

.gitea/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Frontend unit tests
         run: node tests/frontend/unit.test.mjs
 
-      - name: Frontend JSDOM tests (PaneManager + Excalidraw + Plugins + AI + SW + Collab + Mobile + Semantic)
+      - name: Frontend JSDOM tests (PaneManager + Excalidraw + Plugins + AI + SW + Collab + Mobile + Semantic + Desktop)
         run: |
           cd tests/frontend
           if [ -d node_modules ]; then
@@ -50,6 +50,7 @@ jobs:
             node collab.test.mjs
             node mobile-editor.test.mjs
             node semantic-search.test.mjs
+            node desktop.test.mjs
           else
             echo "tests/frontend/node_modules missing - installing jsdom"
             npm install --no-audit --no-fund --silent
@@ -61,6 +62,7 @@ jobs:
             node collab.test.mjs
             node mobile-editor.test.mjs
             node semantic-search.test.mjs
+            node desktop.test.mjs
           fi
 
   # ── Tests ─────────────────────────────────────────────────────────