fix(sandbox-manager): reduce log volume in proxy and infra reconciler

[AiRanthem]

Ⅰ. Describe what this PR does

Reduces unnecessary log noise in the sandbox-manager process by:

1. Proxy handleRefresh: Replaced web.RegisterRoute framework with plain http.HandlerFunc for the internal system port (7789). This endpoint only serves inter-pod route refresh calls and doesn't need request ID generation, panic recovery wrapper, or the full web framework overhead. Log verbosity raised to V(DebugLogLevel+1).

2. Infra refreshRoute: Changed to return a bool indicating whether the route actually changed, so the "route refreshed" debug log only fires on real updates — not on every reconcile cycle where the route is already current.

3. Cache controller: Removed a debug log that fired on every reconcile when no handlers are registered — a normal steady-state condition that doesn't need logging.

4. Bug fix: refreshRoute was using sbx.GetName() to look up routes, but routes are keyed by utils.GetSandboxID(sbx) (namespace + name). Fixed to use the correct key.

Ⅱ. Does this pull request fix one issue?

NONE

Ⅲ. Describe how to verify it

1. Run affected unit tests:

   go test ./pkg/proxy/... ./pkg/cache/controllers/... ./pkg/sandbox-manager/infra/... -count=1

2. Deploy and observe log output — route refresh logs should only appear when state/IP actually changes.

Ⅳ. Special notes for reviews

• The handleRefresh endpoint is internal-only (port 7789, used for peer route sync). Removing the web.RegisterRoute wrapper is safe — Go's net/http server has built-in per-connection panic recovery.
• The sandbox ID bug fix (item 4) is the most impactful change — in multi-namespace deployments, GetName() alone could miss routes that are keyed with the full namespace/name format.

[kruise-bot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.76%. Comparing base (af25739) to head (d6f2c7a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #579      +/-   ##
==========================================
- Coverage   79.78%   79.76%   -0.03%     
==========================================
  Files         202      202              
  Lines       14688    14720      +32     
==========================================
+ Hits        11719    11741      +22     
- Misses       2544     2550       +6     
- Partials      425      429       +4     

Flag	Coverage Δ
unittests	79.76% <100.00%> (-0.03%)	⬇️

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