Draft: MCPRemoteProxy: Add remaining configuration validations

[ChrisJBurns]

Summary

Extends #4024 with the four remaining MCPRemoteProxy configuration validations, each surfacing errors via Kubernetes Events and Status Conditions:

• Remote URL format validation — rejects malformed URLs or unsupported schemes (ftp://, empty host)
• JWKS URL scheme validation — JWKS endpoints must use HTTPS (key material transport)
• Cedar authorization policy syntax — validates inline Cedar policies parse correctly before deployment
• ConfigMap/Secret reference existence — verifies referenced authz ConfigMaps and header Secrets exist in the namespace

All validations follow the foundation pattern from #4024: fail-fast in validateSpec(), set ConfigurationValid=False condition with a specific reason, emit a Warning event, and move the proxy to Failed phase.

No network calls are made — URL validations are format/scheme checks only; ConfigMap/Secret checks are in-cluster reads.

Test plan

• Unit tests for ValidateCedarPolicies (6 cases)
• Unit tests for ValidateRemoteURL (6 cases) and ValidateJWKSURL (5 cases)
• Unit tests for reconciler condition-setting (5 new cases in TestValidateSpecConfigurationConditions)
• Integration tests for status conditions (remote URL, JWKS URL, Cedar syntax, missing ConfigMap, missing Secret)
• Integration tests for event emission (Cedar syntax, missing ConfigMap, missing Secret)
• go build ./cmd/thv-operator/... passes
• golangci-lint passes on changed packages

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 89.56522% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.71%. Comparing base (bc9b534) to head (17d745b).

Files with missing lines	Patch %	Lines
...-operator/controllers/mcpremoteproxy_controller.go	90.58%	7 Missing and 1 partial ⚠️
cmd/thv-operator/pkg/validation/url_validation.go	81.81%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4037      +/-   ##
==========================================
+ Coverage   68.66%   68.71%   +0.04%     
==========================================
  Files         445      447       +2     
  Lines       45343    45456     +113     
==========================================
+ Hits        31136    31236     +100     
- Misses      11802    11812      +10     
- Partials     2405     2408       +3     

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