release: v0.15.0

[wutongci]

Summary

• Normalize empty collection API responses across PostgreSQL repositories and frontend API clients.
• Add defensive normalization for nullable nested collections used by admin, portal, operator, customer, settings, and plugin surfaces.
• Add effective-pricing and model-operations roadmap documentation.
• Bump backend and frontend versions to v0.15.0.

Verification

• go test ./... -count=1
• go vet ./...
• go test -race ./internal/controlplane ./internal/plugins ./internal/server ./internal/appcmd/server -count=1
• npm run test:unit (34 files, 105 tests)
• npm run typecheck
• npm run build
• npm run check:public-doc-links
• npm run check:enterprise-surface
• npm run check:workflow-pipefail
• bash scripts/test-single-origin.sh
• bash scripts/build-release.sh 0.15.0 with an isolated output directory
• bash scripts/test-release-artifacts.sh 0.15.0 with amd64/arm64 archives, checksums, and manifest verified

Review

• Pre-landing review: no SQL safety, concurrency, security, or user-visible regression findings.
• Frontend design scope is limited to nullable collection guards; no layout or styling changes.
• Live-provider, production database, and production object-storage calls were not used.