[VCFN-2809] Add Gateway/ListenerSet controller and DNS service scaffold

[wenyingd]

• Add GatewayReconciler for K8s Gateway API: handles create/update/delete of DNS records via DNSRecordService
• Add ListenerSet event handler to trigger Gateway reconciliation on ListenerSet changes
• Add cmd/main.go wiring for GatewayReconciler and DNSRecordService initialization
• Add DNSRecordService with public API (CreateOrUpdateDNSRecords, DeleteDNSRecordsByOwner, DeleteAllDNSRecordsInGateway, DeleteOrphanedDNSRecordsInGateway, ListGatewayNamespacedName)
• Add DNSRecordStore and DNSZoneStore with indexers for owner UID and gateway namespaced name
• Add unit tests for controller flow and DNS service components; E2E tests are deferred to a follow-up change

AI-Tool-Used: Cursor
AI-Tool-Use-Level: high
AI-Code-Category: production

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.26316% with 141 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.73%. Comparing base (6f7ddad) to head (d52b27b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controllers/gateway/gateway_controller.go	73.62%	73 Missing and 18 partials ⚠️
pkg/nsx/services/dns/store.go	77.96%	17 Missing and 9 partials ⚠️
pkg/controllers/gateway/listenerset_handler.go	60.60%	13 Missing ⚠️
pkg/nsx/services/dns/recordservice.go	88.67%	3 Missing and 3 partials ⚠️
cmd/main.go	0.00%	3 Missing ⚠️
pkg/nsx/services/dns/initialize.go	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1398      +/-   ##
==========================================
- Coverage   76.77%   76.73%   -0.04%     
==========================================
  Files         151      156       +5     
  Lines       21315    21885     +570     
==========================================
+ Hits        16364    16793     +429     
- Misses       3782     3893     +111     
- Partials     1169     1199      +30     

Flag	Coverage Δ
unit-tests	76.73% <75.26%> (-0.04%)	⬇️

Files with missing lines	Coverage Δ
pkg/nsx/services/common/types.go	100.00% <ø> (ø)
pkg/nsx/services/dns/initialize.go	88.88% <88.88%> (ø)
cmd/main.go	0.00% <0.00%> (ø)
pkg/nsx/services/dns/recordservice.go	88.67% <88.67%> (ø)
pkg/controllers/gateway/listenerset_handler.go	60.60% <60.60%> (ø)
pkg/nsx/services/dns/store.go	77.96% <77.96%> (ø)
pkg/controllers/gateway/gateway_controller.go	73.62% <73.62%> (ø)

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