🧪 isolate mihomo integration tests

[luoshuijs]

Summary

• switch integration bootstrap to repo-local PAI_TEST_* config, add cmd/integration-doctor, wrapper scripts, example env, and optional compose dependencies
• replace fixed integration database reuse with per-test MySQL database creation/drop plus optional Redis prefix isolation
• update CI to stop exporting TEST_DATABASE_SOURCE and use the new integration workflow instead

Test Plan

• go test ./...
• go test -tags=integration ./integration/...
• pwsh -File .\scripts\integration.ps1 doctor
• pwsh -File .\scripts\integration.ps1

[codecov]

Codecov Report

❌ Patch coverage is 31.98198% with 151 lines in your changes missing coverage. Please review.
✅ Project coverage is 27.86%. Comparing base (8d853bb) to head (7d4e7db).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/testutil/integrationenv/env.go	34.32%	120 Missing and 12 partials ⚠️
cmd/integration-doctor/main.go	9.52%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #5      +/-   ##
==========================================
+ Coverage   27.52%   27.86%   +0.33%     
==========================================
  Files          25       27       +2     
  Lines        2728     2950     +222     
==========================================
+ Hits          751      822      +71     
- Misses       1859     1998     +139     
- Partials      118      130      +12     

Flag	Coverage Δ
unit	27.86% <31.98%> (+0.33%)	⬆️

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