improve logging and API contracts for simplified deployment

[jimmieme]

Summary

This PR improves AOFS stability and diagnosability for simplified deployment
route regressions.

What Changed

• Added macOS disk usage implementation:
  • repository/storage/disk_usage_darwin.go
• Added API route contract test coverage:
  • routers/routers/routes_contract_test.go
• Updated routing/middleware and API handlers to improve behavior consistency
  and logging.
• Refined multipart/recycled/service/repository code paths for better runtime
  robustness in simplified mode.
• Updated test setup and related config/init code to align with current
  deployment expectations.

Why

Recent restart/regression work exposed two risks:

1. weak contract protection for AOFS API routes,
2. insufficient visibility when troubleshooting request/flow failures.

This PR addresses both by introducing explicit contract tests and improving log
signals.

Validation

• AOFS route contract tests pass.
• Existing smoke/regression scripts continue to pass in simplified deployment
  flow.
• Critical endpoint behavior is explicitly asserted:
  • /space/v1/api/status (no userId) => business success
  • /space/v1/api/file/list (no userId) => parameter error business code

Impact

• Scope is AOFS only.
• No intentional API contract break.
• Improves deployment confidence and debugging efficiency.

Generated-by: Codex