fix(operator): add startup probe to proxyrunner deployment

[gabrielcosi]

Summary

The proxyrunner only opens its 8080 listener once the upstream MCP pod is Ready. With only a LivenessProbe (60s effective budget), cold starts slower than that are killed before the listener is up, which causes spurious proxy restarts during normal rollouts and slow MCP startup.

• Add a StartupProbe to the proxyrunner container in both deploymentForMCPServer and deploymentForMCPRemoteProxy. While the startup probe is active, liveness and readiness are suspended; once it passes, the existing probes take over unchanged.
• Defaults: PeriodSeconds=5, TimeoutSeconds=3, FailureThreshold=18. 90s cold-start budget, 30s above the current effective liveness budget.

Fixes #5299

Type of change

• Bug fix
• New feature
• Refactoring (no behavior change)
• Dependency update
• Documentation
• Other (describe):

Test plan

• Unit tests (task test)
• E2E tests (task test-e2e)
• Linting (task lint-fix)
• Manual testing (describe below)

API Compatibility

• This PR does not break the v1beta1 API, OR the api-break-allowed label is applied and the migration guidance is described above.

Does this introduce a user-facing change?

The proxyrunner pod now has a StartupProbe. Existing liveness and readiness behaviour is unchanged. Net effect: proxy pods no longer restart during slow upstream cold starts.

Special notes for reviewers

Probe parameters are still hardcoded. A proper fix would expose them as overrides on MCPServer.spec.resourceOverrides.proxyDeployment and at the operator level; that is described as a follow-up in the linked issue and intentionally not part of this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.37%. Comparing base (5aa045b) to head (61d7bcd).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5300      +/-   ##
==========================================
+ Coverage   68.36%   68.37%   +0.01%     
==========================================
  Files         620      620              
  Lines       63419    63431      +12     
==========================================
+ Hits        43357    43374      +17     
+ Misses      16823    16817       -6     
- Partials     3239     3240       +1     

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