Accélérer la capture : viewfinder warmup en arrière-plan

- Supprime sleep(0.2) avant capture et viewfinder off inutile
- Déplace activer_viewfinder + chauffer_liveview dans un thread
  daemon après le save, pour retourner la photo immédiatement
- Supprime pause(150ms) frontend entre fin countdown et capture

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/camera.py

@@ -185,14 +185,6 @@ class Camera:
                         log.error("Camera None pendant capture")
                         self.preview_dslr_ok = False
                         return None
-                    try:
-                        cfg = self.camera.get_config()
-                        vf = cfg.get_child_by_name("viewfinder")
-                        vf.set_value(0)
-                        self.camera.set_config(cfg)
-                        time.sleep(0.2)
-                    except Exception:
-                        pass
                     log.info(f"Déclenchement capture DSLR (tentative {attempt+1}/3)")
                     chemin_camera = self.camera.capture(gp.GP_CAPTURE_IMAGE)
                     fichier_camera = gp.CameraFile()
@@ -201,8 +193,7 @@ class Camera:
                     )
                     tmp_path = str(chemin_dest) + ".tmp"
                     fichier_camera.save(tmp_path)
-                self.activer_viewfinder()
-                self._chauffer_liveview()
+                threading.Thread(target=self._post_capture_warmup, daemon=True).start()
                 from PIL import ImageOps as PILImageOps
                 img = PILImageOps.exif_transpose(PILImage.open(tmp_path))
                 if img.width > 4000:
@@ -225,6 +216,10 @@ class Camera:
                 self.preview_dslr_ok = False
                 return None
 
+    def _post_capture_warmup(self):
+        self.activer_viewfinder()
+        self._chauffer_liveview()
+
     def _chauffer_liveview(self, tentatives: int = 8, pause: float = 0.15):
         """Consomme les premieres frames LiveView juste apres la remontee du miroir
         (souvent en erreur ~1-2s le temps que l'AF/capteur se stabilise), pendant

frontend/index.html

@@ -917,7 +917,7 @@
 
   <script src="/js/websocket.js?v=16"></script>
   <script src="/js/app.js?v=18"></script>
-  <script src="/js/camera.js?v=15"></script>
+  <script src="/js/camera.js?v=16"></script>
   <script src="/js/effects.js?v=4"></script>
   <script src="/js/gallery.js?v=3"></script>
   <script src="/js/share.js?v=8"></script>

frontend/js/camera.js

@@ -253,7 +253,6 @@ async function lancerCapture() {
     lancerPreview();         // Miroir live pendant le compte à rebours
     await compteARebours();
     arreterPreview();
-    await pause(150);
 
     const promesseCapture = apiPost('/api/capturer').catch(() => null);
     let resultat = await promesseCapture;