feat: photo quality improvements

- webcam capture resolution/quality configurable in admin settings (defaults 640x480 / 0.92)
- enhance photo modal in journal: original vs preview with sliders (brightness, contrast, saturation, sharpen) and auto-levels button
- new endpoint PUT /api/entries/:id/photo/enhance replaces photo, cleans old file and thumb
- sharper HEIC conversion (0.92) and webp thumbnails (85)
- worker: fail explicitly on empty AI response

worker.js

@@ -128,7 +128,12 @@ function createEntryAutoChecker({ pool, getSetting, logAudit, aiUrl, defaultProm
       });
       if (!res.ok) throw new Error(`AI service error: ${res.status}`);
       const data = await res.json();
-      return (data.choices?.[0]?.message?.content || '').trim();
+      const choice = data.choices && data.choices[0];
+      const content = (choice && choice.message && choice.message.content || '').trim();
+      if (!content) {
+        throw new Error(`Модель вернула пустой ответ (finish_reason=${choice && choice.finish_reason || 'unknown'})`);
+      }
+      return content;
     } finally {
       clearTimeout(timer);
     }