feat(imggen): генерация картинок ИИ (FLUX.1) — ассистент, флэшкарты, редактор уроков

Бэкенд /api/imggen (status/generate, CF Workers AI, cooldown+дневной лимит).
Переиспользуемый модал LS.imagePromptModal (js/imggen.js).
Квантик: режим «Нарисовать» в чате (inline).
Флэшкарты: кнопка «ИИ» в блоке картинки карточки.
Редактор уроков: кнопка «Сгенерировать» в блоке изображения.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/api.js

@@ -1050,7 +1050,7 @@ window.LS = {
   crAdminGetAllHistory, crAdminGetTeachersList,
   listMaterials, saveMaterial, updateMaterial, deleteMaterial, shareMaterial, getActivity,
   createMaterialCollection, updateMaterialCollection, deleteMaterialCollection,
-  assistantContext, assistantSeen, assistantDismiss, assistantSettings, assistantAsk, assistantFlashcards, assistantFeedback, assistantMemory, assistantMemoryClear,
+  assistantContext, assistantSeen, assistantDismiss, assistantSettings, assistantAsk, assistantFlashcards, assistantFeedback, assistantMemory, assistantMemoryClear, imageGen, imageGenStatus,
   adminGetAssistant, adminSaveAssistant, adminTestAssistant, adminReindexTextbooks,
   adminSaveProvider, adminDeleteProvider, adminSetActiveProvider, adminAssistantModels,
   fcListDecks, fcCreateDeck, fcAddCard,
@@ -1279,6 +1279,8 @@ async function assistantFlashcards(text, title) { return req('POST', '/assistant
 async function assistantFeedback(rating, q) { return req('POST', '/assistant/feedback', { rating, q: q || undefined }); }
 async function assistantMemory()      { return req('GET',    '/assistant/memory'); }
 async function assistantMemoryClear(id) { return req('DELETE', '/assistant/memory' + (id ? '/' + id : '')); }
+async function imageGen(prompt)       { return req('POST',   '/imggen', { prompt }); }
+async function imageGenStatus()       { return req('GET',    '/imggen/status'); }
 async function adminGetAssistant()   { return req('GET',  '/admin/assistant'); }
 async function adminSaveAssistant(d) { return req('PUT',  '/admin/assistant', d); }
 async function adminTestAssistant(d) { return req('POST', '/admin/assistant/test', d || {}); }