fix(web): defer react-scan loader

[lyzno1]

Summary

• defer the dev-only react-scan script until after hydration
• document that react-scan recommends beforeInteractive, but it can conflict with Dify's inline attribution bootstrap during dev hydration

Tests

• Not run (per request).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.82%. Comparing base (5c1cfe6) to head (54e820e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #36920   +/-   ##
=======================================
  Coverage   85.82%   85.82%           
=======================================
  Files        4565     4565           
  Lines      223439   223439           
  Branches    41135    41135           
=======================================
  Hits       191767   191767           
  Misses      27968    27968           
  Partials     3704     3704           

Flag	Coverage Δ
dify-ui	95.57% <ø> (ø)
web	86.48% <ø> (ø)

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