add feature flags to enable/disable controller groups

[amirejaz]

Summary

Adds operator-side feature flags to complement the CRD installation flags from #2809, allowing users to conditionally enable/disable controller groups at runtime.

Changes

• Add ENABLE_SERVER, ENABLE_REGISTRY, ENABLE_VMCP environment variables in main.go
• Refactor setupControllersAndWebhooks to conditionally start controllers based on flags
• Add dependency checking (VMCP requires Server to be enabled)
• Wire feature flags through Helm values (operator.features.server/registry/virtualMCP)
• Update deployment template to pass environment variables

Usage

Skip Virtual MCP controllers (matches crds.install.virtualMcp=false):

helm install operator ... --set operator.features.virtualMCP=false

Related

Complements #2809 (CRD installation feature flags)

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.16%. Comparing base (dda67b9) to head (dc1442a).

Files with missing lines	Patch %	Lines
cmd/thv-operator/main.go	25.00%	45 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3093      +/-   ##
==========================================
- Coverage   57.21%   57.16%   -0.05%     
==========================================
  Files         341      341              
  Lines       34089    34145      +56     
==========================================
+ Hits        19503    19519      +16     
- Misses      12972    13019      +47     
+ Partials     1614     1607       -7     

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[yrobla]

added a comment
also, it's missing tests and documentation

[yrobla]

why does it depend only on vmcp enabled? and not on server?