feat(image): inline upload-error feedback parity with FontManager

The image upload handler had `try/finally` without `catch`, so failures
(non-image MIME, oversize, decode error, GFA exception) propagated as
unhandled rejections with no user signal. Add `uploadFailed` state and a
small inline hint matching FontManager's pattern.

Author: u8array

src/locales/ar.ts

@@ -256,6 +256,7 @@ const ar = {
       selectImage: 'اختر صورة…',
       upload: 'رفع صورة',
       uploading: 'جارٍ الرفع…',
+      uploadError: 'تعذر تحميل الصورة',
       preview: 'معاينة',
       widthDots: 'العرض (نقاط)',
       threshold: 'عتبة أحادية',

src/locales/bg.ts

@@ -256,6 +256,7 @@ const bg = {
       selectImage: 'Изберете изображение…',
       upload: 'Качване на изображение',
       uploading: 'Качване…',
+      uploadError: 'Изображението не може да бъде заредено',
       preview: 'Преглед',
       widthDots: 'Ширина (точки)',
       threshold: 'Моно праг',

src/locales/cs.ts

@@ -256,6 +256,7 @@ const cs = {
       selectImage: 'Vybrat obrázek…',
       upload: 'Nahrát obrázek',
       uploading: 'Nahrávání…',
+      uploadError: 'Obrázek nelze načíst',
       preview: 'Náhled',
       widthDots: 'Šířka (body)',
       threshold: 'Mono práh',

src/locales/da.ts

@@ -256,6 +256,7 @@ const da = {
       selectImage: 'Vælg billede…',
       upload: 'Upload billede',
       uploading: 'Uploader…',
+      uploadError: 'Kunne ikke indlæse billede',
       preview: 'Forhåndsvisning',
       widthDots: 'Bredde (punkter)',
       threshold: 'Mono-tærskel',

src/locales/de.ts

@@ -276,6 +276,7 @@ const de = {
       selectImage: 'Bild auswählen…',
       upload: 'Bild hochladen',
       uploading: 'Hochladen…',
+      uploadError: 'Bild konnte nicht geladen werden',
       preview: 'Vorschau',
       widthDots: 'Breite (Punkte)',
       threshold: 'Mono-Schwellenwert',

src/locales/el.ts

@@ -256,6 +256,7 @@ const el = {
       selectImage: 'Επιλογή εικόνας…',
       upload: 'Μεταφόρτωση εικόνας',
       uploading: 'Μεταφόρτωση…',
+      uploadError: 'Αδυναμία φόρτωσης εικόνας',
       preview: 'Προεπισκόπηση',
       widthDots: 'Πλάτος (κουκκίδες)',
       threshold: 'Κατώφλι mono',

src/locales/en.ts

@@ -276,6 +276,7 @@ const en = {
       selectImage: 'Select image…',
       upload: 'Upload image',
       uploading: 'Uploading…',
+      uploadError: 'Could not load image',
       preview: 'Preview',
       widthDots: 'Width (dots)',
       threshold: 'Mono threshold',

src/locales/es.ts

@@ -256,6 +256,7 @@ const es = {
       selectImage: 'Seleccionar imagen…',
       upload: 'Subir imagen',
       uploading: 'Subiendo…',
+      uploadError: 'No se pudo cargar la imagen',
       preview: 'Vista previa',
       widthDots: 'Ancho (puntos)',
       threshold: 'Umbral mono',

src/locales/et.ts

@@ -256,6 +256,7 @@ const et = {
       selectImage: 'Vali pilt…',
       upload: 'Laadi pilt üles',
       uploading: 'Üleslaadimine…',
+      uploadError: 'Pildi laadimine ebaõnnestus',
       preview: 'Eelvaade',
       widthDots: 'Laius (punktid)',
       threshold: 'Mono lävi',

src/locales/fa.ts

@@ -256,6 +256,7 @@ const fa = {
       selectImage: 'انتخاب تصویر…',
       upload: 'بارگذاری تصویر',
       uploading: 'در حال بارگذاری…',
+      uploadError: 'بارگذاری تصویر ممکن نشد',
       preview: 'پیش‌نمایش',
       widthDots: 'عرض (نقاط)',
       threshold: 'آستانه تک‌رنگ',