Add Kindle EPUB compatibility fixer

Introduce an optional Kindle EPUB compatibility fixer and integrate it into the ebook organization flow. Adds a new config key (ebook_kindle_fix_enabled, default false), a settings API update, and a UI toggle (visible when preferred format is EPUB). Implements src/lib/utils/epub-fixer.ts (uses adm-zip and cheerio) to apply fixes: add UTF-8 XML declarations, remove body/#bodymatter fragments from links, validate/normalize dc:language, and remove stray <img> tags without src. organize-files.processor now detects EPUB downloads, runs the fixer (produces a temp fixed EPUB), uses the fixed file for organization, logs fixes, and cleans up temporary files; fix failures are non-blocking and the original download is preserved. Adds dependencies adm-zip and @types/adm-zip and updates documentation and types/UI to expose the new setting. Also includes helper functions to detect EPUB paths in downloads.

package.json

@@ -18,6 +18,7 @@
   "dependencies": {
     "@heroicons/react": "^2.2.0",
     "@prisma/client": "^6.19.0",
+    "adm-zip": "^0.5.16",
     "axios": "^1.7.2",
     "bcrypt": "^5.1.1",
     "bull": "^4.12.0",
@@ -42,6 +43,7 @@
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
     "@testing-library/jest-dom": "^6.9.1",
+    "@types/adm-zip": "^0.5.6",
     "@testing-library/react": "^16.3.1",
     "@testing-library/user-event": "^14.6.1",
     "@types/bcrypt": "^5.0.2",