feat(desktop): manifeste de mise a jour latest.json + builds locaux signes (#77)

- scripts/updater_manifest.py : construit latest.json (version, pub_date, platforms Windows/Linux avec signature .sig et URLs des assets).

- publish_release.py : genere latest.json, upload des .sig + latest.json, rappel de commit.

- tauri.conf.json : endpoint updater -> raw/branch/main/desktop/latest.json.

- build-windows.bat / build-linux.sh : detection automatique de obsigate-updater.key (signature) ou repli non signe.

- .gitignore : ignore desktop/key/ ; tests/test_updater_manifest.py (8 tests).

desktop/build-windows.bat

@@ -51,12 +51,23 @@ xcopy /E /I /Q /Y "..\backend" "backend"
 xcopy /E /I /Q /Y "..\frontend" "frontend"
 echo ✅ Staged
 
+REM ── 2c. Clé de signature des mises à jour (updater Tauri) ──────
+set "SIGN_CONFIG="
+if exist "obsigate-updater.key" (
+    set /p TAURI_SIGNING_PRIVATE_KEY=<obsigate-updater.key
+    echo [2c/6] Cle updater trouvee - artefacts .sig actives
+) else (
+    > updater-off.json echo {"bundle":{"createUpdaterArtifacts":false}}
+    set "SIGN_CONFIG=--config updater-off.json"
+    echo [2c/6] Cle updater absente - build sans .sig
+)
+
 REM ── 3. Build Tauri ────────────────────────────────────────────
 echo [3/6] Building Tauri application (NSIS + MSI installers)...
-cargo tauri build --target x86_64-pc-windows-msvc --bundles nsis,msi
+cargo tauri build --target x86_64-pc-windows-msvc --bundles nsis,msi %SIGN_CONFIG%
 if errorlevel 1 (
     echo ⚠️ Standard bundle build failed, trying fallback to NSIS only...
-    cargo tauri build --target x86_64-pc-windows-msvc --bundles nsis
+    cargo tauri build --target x86_64-pc-windows-msvc --bundles nsis %SIGN_CONFIG%
     if errorlevel 1 (
         echo ❌ Build failed!
         goto :cleanup
@@ -77,6 +88,7 @@ REM ── 5. Nettoyer les dossiers stagés ────────────
 echo [5/6] Cleaning up staged dirs...
 if exist "backend" rmdir /s /q "backend"
 if exist "frontend" rmdir /s /q "frontend"
+if exist "updater-off.json" del /q "updater-off.json"
 echo ✅ Cleaned
 
 REM ── 6. Résultats ───────────────────────────────────────────────