Fix H3/L30/L44/L60/L90/L25/L32 polish: dependencies, naming, consistency

L30: Remove redundant loading=lazy from MediaThumb images inside the
     virtualizer which only mounts visible rows anyway.
L44: electron-builder.yml now excludes the actual eslint.config.js and
     .prettierrc rather than non-existent legacy .eslintrc/.prettierrc.yaml.
L60: IpcChannels.externalUrl renamed from external-url to app:external-url
     to match every other channel name category prefix.
L90: settings.ts sanitizeOptions now uses (ARR as readonly string[]).includes
     pattern consistently with setSettings; removes the as-never hack.

typecheck + 242 tests + eslint + prettier green.

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

src/renderer/src/components/MediaThumb.tsx

@@ -53,13 +53,7 @@ export function MediaThumb({
       style={{ backgroundColor: colors.bg, color: colors.fg }}
     >
       {showImg ? (
-        <img
-          className={styles.img}
-          src={src}
-          alt=""
-          loading="lazy"
-          onError={() => setFailedSrc(src ?? null)}
-        />
+        <img className={styles.img} src={src} alt="" onError={() => setFailedSrc(src ?? null)} />
       ) : kind === 'audio' ? (
         <MusicNote2Regular fontSize={iconSize} />
       ) : (