feat: #78 Excalidraw finitions + #67 push + #68 health-detailed + #77 desktop jumplist

#78 Excalidraw — finitions B5/C8/F2/F3
- backend/indexer.py: port Python pur de lz-string decompressFromBase64 (bitsPerChar=6, resetValue=32) validé contre 4 fixtures JS truth (texte accentué, edge cases) — remplace le stub base64 non-fonctionnel
- B5 indexation: .excalidraw.md (format plugin Obsidian) maintenant décompressé côté Python → texte indexé pour recherche TF-IDF
- 7 nouveaux tests B5 dans tests/test_excalidraw.py (13/13 total)
- F2: excalidraw-viewer.test.mjs enregistré dans CI (lint job)
- F3: tests/e2e/excalidraw.spec.js (9 specs — ouverture .excalidraw/.excalidraw.md, création via modale/menu contextuel, toolbar, thème, pop-out, recherche)
- Fixtures test_vault/diagram.excalidraw + diagram.excalidraw.md

#67 Push notifications (Web Push API + VAPID)
- backend/push.py: router + VAPID keys + send_push_notification (pywebpush>=2.3.0)
- frontend/js/push.js: subscription UI + service worker integration
- tests/test_push.py: 10 tests (subscribe/list/unsubscribe/vapid key)
- requirements.txt + sw.js + locales push strings

#68 Health check enrichi
- backend/main.py: GET /api/health/detailed (admin) — memory/cpu/disk/backups/index/SSE connections
- backend/indexer.py: _last_full_index_ts tracking
- tests/conftest.py: admin_client fixture
- tests/test_api_main.py: 3 nouveaux tests health detailed

#77 Desktop jumplist
- desktop/src/jumplist.rs: Windows jumplist integration
- Cargo.toml/lock + capabilities + main.rs
- frontend/js/desktop.js: Tauri bridge (isTauriEnv, invoke, getSystemTheme, syncSystemTheme, shouldShowWizard, crash banner)
- tests/frontend/desktop.test.mjs: 21 tests JSDOM (détection, invoke degradation, theme gating, wizard, crash banner)
- tests/frontend/unit.test.mjs: desktop.js whitelisted (standalone global reader)

# Frontend & CI
- frontend/sw.js: réécriture complète (precache + push event handlers + offline)
- frontend/index.html: section push dans settings + about repositionné
- frontend/js/app.js: initDesktopIntegration + initPush
- CI .gitea/workflows/ci.yml: excalidraw-viewer.test.mjs ajouté au lint job

All checks: ruff clean, 552 backend tests pass, 9 frontend unit, 5 excalidraw-viewer, 21 desktop, 9 pane-manager, validate-imports 33 modules.

frontend/index.html

@@ -1449,6 +1449,7 @@
 <li><a href="#cfg-themes" class="help-nav-link" data-i18n="settings.themes"></a></li>
 <li><a href="#cfg-profile" class="help-nav-link" data-i18n="settings.profile"></a></li>
 <li><a href="#cfg-security" class="help-nav-link" data-i18n="settings.security"></a></li>
+<li><a href="#cfg-push" class="help-nav-link" data-i18n="config.section_push">Notifications push</a></li>
 <li><a href="#cfg-about" class="help-nav-link" data-i18n="settings.about"></a></li>
 <li><a href="#cfg-webhooks" class="help-nav-link" data-i18n="config.section_webhooks"></a></li>
 <li><a href="#cfg-partages-publics" class="help-nav-link" data-i18n="config.section_shares"></a></li>
@@ -2185,11 +2186,29 @@
                                 </div>
                             </section>
 
-                            <!-- À propos -->
-                            <section
-                                class="config-section help-section"
-                                id="cfg-about"
-                            >
+                                                        <!-- Notifications push -->
+                                                        <section
+                                                            class="config-section help-section"
+                                                            id="cfg-push"
+                                                        >
+                                                            <h2 data-i18n="config.section_push">🔔 Notifications push</h2>
+                                                            <p class="config-description">
+                                                                Recevez des notifications web push
+                                                                lorsque des fichiers changent dans vos
+                                                                vaults, même si ObsiGate n'est pas ouvert.
+                                                            </p>
+                                                            <div id="push-settings">
+                                                                <div class="config-diag-loading" data-i18n="common.loading">
+                                                                    Chargement...
+                                                                </div>
+                                                            </div>
+                                                        </section>
+
+                                                        <!-- À propos -->
+                                                        <section
+                                                            class="config-section help-section"
+                                                            id="cfg-about"
+                                                        >
                                 <h2 data-i18n="auto.a3319169">📦 À propos</h2>
                                 <div
                                     id="config-about"