chore: 3-loop maintenance pass — i18n coverage, dead-code cleanup, JSON-LD locale fix

Loop 1 — dead code & i18n base:
- Remove empty src/lib/hooks/ directory.
- Delete unused public/images/samples/example.jpg (~158KB) and
  public/scenes/thumbnails/* (6 files, ~70KB) — DofScene `thumbnail`
  field was defined but never read in any UI.
- Drop the dead `thumbnail` field from DofScene.
- i18n LanguageSwitcher's "Change language" / "Select language"
  aria-labels (shown on every page in every locale).
- i18n the perspective-compression simulator's "Sensor" aria-label.

Loop 2 — i18n templates, dead fields, JSON-LD locale awareness:
- Add ICU-templated controls aria-labels (apertureValue,
  focalLengthValue, subjectDistanceValue, sweetSpotValue) and wire
  them into ApertureField, FocalLengthField, and
  CompressionControls — replaces hardcoded "Aperture: f/2.8" /
  "Focal length: 50mm" / "Subject distance: 12.5 ft" / "Sweet spot:
  f/8" templates.
- Remove the dead `altText` field from Scene (and its test) — it
  was never read by any consumer.
- Fix glossary FAQPage JSON-LD: was generating hardcoded English
  "What is X in photography?" for every locale; now uses a
  translatable `questionTemplate` and adds the missing `inLanguage`
  field. Mirror the fix on privacy/terms/about/contact JSON-LD —
  they now include `inLanguage` and a locale-prefixed `url`,
  preventing every locale's structured data from claiming the
  English `/privacy` URL.
- Add `apsh` (APS-H) translation key — was a missing sensor falling
  through to the English fallback name.
- AdUnit: drop a redundant `if (ins)` guard after an early-return
  null check on the same ref.

Loop 3 — final i18n + memory leak:
- i18n the FaqSection heading "Frequently Asked Questions" — high-
  impact since it renders on every tool page in every locale.
- Add `loading="lazy"` + `decoding="async"` to exposure-simulator
  scene thumbnails.
- Fix a small blob URL leak in frame-studio: `URL.createObjectURL`
  was created on each handleFile call and never revoked, so each
  upload after the first leaked the previous URL until GC. Now we
  revoke once the Image has decoded.

All 872 unit tests, 122 chromium smoke specs, and 85 chromium tool
e2e specs pass. Type-check and lint clean. Translation coverage
verified across all 31 locales; no hard English leaks introduced.

Author: kevinkiklee

public/images/samples/example.jpg

@@ -33,7 +33,8 @@ export default async function AboutPage({ params }: { params: Promise<{ locale:
     '@context': 'https://schema.org',
     '@type': 'AboutPage',
     name: t('title'),
-    url: 'https://www.phototools.io/about',
+    url: `https://www.phototools.io/${locale}/about`,
+    inLanguage: locale,
   }
 
   return (

public/scenes/thumbnails/architecture.jpg

@@ -25,7 +25,8 @@ export default async function ContactPage({ params }: { params: Promise<{ locale
     '@context': 'https://schema.org',
     '@type': 'ContactPage',
     name: t('title'),
-    url: 'https://www.phototools.io/contact',
+    url: `https://www.phototools.io/${locale}/contact`,
+    inLanguage: locale,
   }
 
   return (

public/scenes/thumbnails/cafe.jpg

@@ -47,6 +47,8 @@ export function ExposurePreview({ aperture, shutterSpeed, iso }: ExposurePreview
                 alt={label}
                 width={48}
                 height={32}
+                loading="lazy"
+                decoding="async"
               />
             </button>
             )
@@ -62,6 +64,7 @@ export function ExposurePreview({ aperture, shutterSpeed, iso }: ExposurePreview
               src={currentScene.assets.photo}
               alt={t(currentScene.labelKey as Parameters<typeof t>[0])}
               className={styles.fallbackImg}
+              decoding="async"
             />
             <p>{error}. {t('imageEffectsUnavailable')}</p>
           </div>