refactor(web): replace lamejs mp3 encoding

[hyoban]

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Summary

Fixes #38172

• Replace lamejs voice input MP3 encoding with Mediabunny and @mediabunny/mp3-encoder.
• Encode recorder PCM data through AudioSampleSource and Mp3OutputFormat while preserving the audio/mp3 upload behavior.
• Remove the local lamejs type declarations and update voice input tests for mono, stereo, native encoder detection, and invalid channel data.

Screenshots

Before	After
N/A	N/A

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran make lint && make type-check (backend) and cd web && pnpm exec vp staged (frontend) to appease the lint gods

Validation

• pnpm -C web test app/components/base/voice-input/__tests__/utils.spec.ts
• pnpm -C web test app/components/base/voice-input/__tests__/index.spec.tsx
• pnpm -C web type-check
• pnpm -C web lint:tss
• pnpm -C web exec tsx -e "..." smoke test for real Mediabunny MP3 encoding: audio/mp3 3060

pnpm -C web exec vp staged was attempted, but this repository currently reports: No "staged" config found in vite.config.ts.

From Codex

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.38%. Comparing base (49a92f0) to head (b252f4f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #38173      +/-   ##
==========================================
+ Coverage   85.32%   85.38%   +0.05%     
==========================================
  Files        4967     5122     +155     
  Lines      258518   262867    +4349     
  Branches    49059    50117    +1058     
==========================================
+ Hits       220593   224442    +3849     
- Misses      33632    34132     +500     
  Partials     4293     4293              

Flag	Coverage Δ
cli	88.45% <ø> (?)
dify-ui	94.93% <ø> (ø)
web	85.05% <100.00%> (+<0.01%)	⬆️

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