feat(blueprints): add import apply

[YOMXXX]

Summary

• Add POST /api/blueprints/apply for owner/admin-only workspace blueprint imports.
• Reuse the preview plan to block missing runtime/env/conflict cases before opening a write transaction.
• Create skills/files, agents, agent-skill links, squads, and squad members transactionally; repeat applies reuse existing resources by name.
• Persist only manifest-declared env schema values and keep MCP/runtime config redacted on import.

Stack note

This is the third PR in the workspace blueprint stack:

1. feat(blueprints): add workspace blueprint export #3132 adds blueprint export.
2. feat(blueprints): add import preview #3133 adds import preview.
3. This PR adds import apply.

GitHub cannot target a fork branch as the upstream base here, so this PR is opened against main and its diff temporarily includes the earlier stack until #3132 and #3133 land. Please review/merge in that order.

Tests

• go test -count=1 ./internal/blueprint ./internal/handler -run 'TestBuildManifest|TestValidateManifest|TestPreviewManifest|TestExportBlueprint|TestPreviewBlueprint|TestApplyBlueprint'
• go test -count=1 ./cmd/server -run '^$'

Known local verification gap

• go test -count=1 ./internal/blueprint ./internal/handler ./cmd/server is blocked in this local database/environment by existing failures unrelated to this PR: missing contact_sales_inquiry relation and readiness endpoints returning 503.

[vercel]

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