Replace ReferencingServers with ReferencingWorkloads on MCPExternalAuthConfig

[ChrisJBurns]

Summary

Migrates MCPExternalAuthConfig from ReferencingServers []string to ReferencingWorkloads []WorkloadReference, aligning it with the structured workload reference pattern established on MCPOIDCConfig in #4492. This enables the status field to distinguish between different workload kinds (MCPServer, VirtualMCPServer, MCPRemoteProxy) rather than assuming all referencing workloads are MCPServers.

Partial fix for #4491

Type of change

• Enhancement to an existing feature

Changes

File	Changes
mcpexternalauthconfig_types.go	Replace ReferencingServers []string with ReferencingWorkloads []WorkloadReference, update printer column
mcpexternalauthconfig_controller.go	Add findReferencingWorkloads(), update reconcile/deletion logic to use structured refs with DeletionBlocked condition
mcpexternalauthconfig_controller_test.go	Update assertions to use WorkloadReference{Kind, Name} structs
mcpexternalauthconfig_controller_integration_test.go	Update assertions to use WorkloadReference{Kind, Name} structs
Generated files	Regenerated deepcopy, CRD YAML manifests

Test plan

• Unit tests updated and passing (go test ./cmd/thv-operator/controllers/... -run MCPExternalAuthConfig)
• Integration tests updated
• CRD manifests regenerated via task gen

Special notes for reviewers

Follows the exact pattern from #4492 (MCPOIDCConfig migration). MCPToolConfig migration is in a separate PR. MCPTelemetryConfig will follow separately.

Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 41.17647% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.07%. Comparing base (a78d9bf) to head (d7d12b9).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...or/controllers/mcpexternalauthconfig_controller.go	41.17%	37 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4507      +/-   ##
==========================================
+ Coverage   69.04%   69.07%   +0.02%     
==========================================
  Files         502      502              
  Lines       51909    51950      +41     
==========================================
+ Hits        35843    35886      +43     
+ Misses      13279    13277       -2     
  Partials     2787     2787              

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