feat(amplitude): integrate AmplitudeProvider and refactor initialization logic

[CodingOnStar]

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Summary

• Added AmplitudeProvider to the main layout for analytics tracking.
• Removed redundant AmplitudeProvider instances from common layouts.
• Introduced a new init module to handle Amplitude initialization and session replay plugin setup.
• Updated tests to ensure proper initialization behavior and prevent multiple initializations.

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

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.50%. Comparing base (8f070f2) to head (b6a0062).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
web/app/components/base/amplitude/init.ts	92.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #35415      +/-   ##
==========================================
- Coverage   85.50%   85.50%   -0.01%     
==========================================
  Files        4433     4434       +1     
  Lines      206943   206953      +10     
  Branches    38519    38521       +2     
==========================================
+ Hits       176940   176948       +8     
- Misses      26899    26901       +2     
  Partials     3104     3104              

Flag	Coverage Δ
dify-ui	92.85% <ø> (ø)
web	86.34% <92.85%> (-0.01%)	⬇️

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