Add language config and locale-aware parsing

Introduce centralized language configuration and wire locale-aware behavior across scraping and ranking. Adds src/lib/constants/language-config.ts with per-language scraping rules, stop words, and character replacements; replaces AudibleRegion.isEnglish with a language field in types and AUDIBLE_REGIONS. Update AudibleService, ebook scraper, processors, and API routes to use getLanguageForRegion so Anna's Archive searches, scraping selectors, runtime/rating parsing, and ranking use language-specific params and filters. Extend ranking algorithm to accept stopWords and characterReplacements and apply them during normalization and matching. Update UI selects to mark non-English regions and adjust tests accordingly.

src/app/setup/steps/BackendSelectionStep.tsx

@@ -115,11 +115,11 @@ export function BackendSelectionStep({
         >
           {Object.values(AUDIBLE_REGIONS).map((region) => (
             <option key={region.code} value={region.code}>
-              {region.name}{!region.isEnglish ? ' *' : ''}
+              {region.name}{region.language !== 'en' ? ' *' : ''}
             </option>
           ))}
         </select>
-        {AUDIBLE_REGIONS[audibleRegion]?.isEnglish === false && (
+        {AUDIBLE_REGIONS[audibleRegion]?.language !== 'en' && (
           <div className="bg-amber-50 dark:bg-amber-900/20 rounded-lg p-4 border border-amber-200 dark:border-amber-800 mt-2">
             <div className="flex gap-3">
               <svg