feat(brand): brand-driven hook music + local whoosh SFX - #68

- Fix next/image mock to avoid document.createElement usage
- Replace DOM manipulation with jest.fn() factory function
- Resolves Jest test failures in pre-commit hook

hook-music.mp3 is intentionally absent (user-supplied per README). The file
name was hardcoded as the default hookMusicSrc prop, causing getAudioDurationInSeconds
to eagerly fetch it and produce a 404 on every ShortFormClip preview.

Remove the default from both components and the Root.tsx defaultProps so the
guard (if props.hookMusicSrc) correctly skips the fetch when no file is provided.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Add hookMusic?: string to Brand.audio. calculateMetadata and
calculateShortMetadata now fetch the brand JSON when no explicit
hookMusicSrc prop is provided and read brand.audio.hookMusic as the
fallback. The resolved path is written back into overrideProps so the
component renders the <Audio> tag correctly.

Set ragtech hookMusic to /sounds/jazz-cafe-music.mp3 in brand.json.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

@remotion/sfx exports whoosh as https://remotion.media/whoosh.wav, which
the browser blocks with a CORS error in dev. Downloaded the file to
public/sounds/whoosh.wav and replaced the import with staticFile().

Also extend the ESLint Remotion override from remotion/*.tsx to
remotion/**/*.tsx so components in subdirectories are not linted under
Next.js rules (no-img-element does not apply in Remotion's render context).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

…version

- Restructure .babelrc so next/babel only applies in development/production;
  test env uses explicit preset-env with modules:commonjs, preset-react, preset-typescript.
  next/babel's internal preset-env was overriding modules:commonjs, leaving import
  statements untransformed and causing SyntaxError in jest-runtime.
- Downgrade babel-jest from ^30.2.0 to 29.7.0 to match jest@^29.7.0 in use.
- Expand Composition and ShortFormClip tests to cover brand audio resolution paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

B1: add hookMusic? to Brand.audio spec in PRODUCTION_REFACTOR_PLAN.md
B2: fix brand.json backgroundMusic path (background-music.mp3 → jazz-cafe-music.mp3)
W1: remove vacuous eslint-disable-next-line; type next/image mock explicitly
W2: add Saloni to brand.json hosts array with correct role and colour
W3: fix team imgSrc extensions to .PNG to match actual files on disk

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>