✨ add generic platform credential operations

[luoshuijs]

Summary

• implement generic platform credential put, refresh, and delete RPCs on mihomo service
• tighten binding-aware ticket validation, scope enforcement, and transactional rebind behavior
• support account-center orchestration through the shared platform contract instead of service-local assumptions

Test Plan

• go test ./...

[codecov]

Codecov Report

❌ Patch coverage is 54.82456% with 103 lines in your changes missing coverage. Please review.
✅ Project coverage is 27.52%. Comparing base (6dede6f) to head (ec10438).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/service/platform_service_adapter.go	35.05%	47 Missing and 16 partials ⚠️
internal/usecase/management_usecase.go	64.28%	6 Missing and 4 partials ⚠️
internal/usecase/bind_usecase.go	83.92%	5 Missing and 4 partials ⚠️
internal/data/credential_repo.go	12.50%	6 Missing and 1 partial ⚠️
internal/data/profile_repo.go	16.66%	4 Missing and 1 partial ⚠️
internal/data/tx_context.go	33.33%	3 Missing and 1 partial ⚠️
internal/data/device_repo.go	0.00%	3 Missing ⚠️
cmd/platform-mihomo-service/main.go	0.00%	1 Missing ⚠️
internal/usecase/scope_guard.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
+ Coverage   25.52%   27.52%   +2.00%     
==========================================
  Files          24       25       +1     
  Lines        2547     2728     +181     
==========================================
+ Hits          650      751     +101     
- Misses       1798     1859      +61     
- Partials       99      118      +19     

Flag	Coverage Δ
unit	27.52% <54.82%> (+2.00%)	⬆️

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