feat(admin): dashboard/API foundation with React + Vite client

[Vardominator]

Summary

• add admin API foundation under src/admin with auth/RBAC, org/instance/agent CRUD, onboarding validate/commit flows, provider key encryption/redaction, usage/cost tracking, org settings, inventory import/export, runtime bridge endpoints, and audit events
• add stack/dev orchestration commands for one-command bring-up and status (stack up/down/status, dev up/down/logs)
• add React + Vite dashboard app under dashboard/ (served from /admin) with collapsible navigation and pages for onboarding, overview, agent details, settings, providers, and audit
• keep backend/core code in top-level src/ and isolate UI toolchain in dashboard/
• update docs/README for architecture, local dev, and deployment/testing workflow
• add admin API/store/stack tests

Validation

• bun run typecheck
• bun test
• bun run dashboard:build
• bun run build:all
• node dist/cli.js validate
• node dist/cli.js policy validate
• set -a; source .env; set +a; node dist/cli.js stack up
• set -a; source .env; set +a; node dist/cli.js health --instance core-human

[codecov]

Codecov Report

❌ Patch coverage is 66.73084% with 864 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/admin/api.ts	66.79%	434 Missing ⚠️
src/admin/stack.ts	39.08%	187 Missing ⚠️
src/admin/store.ts	77.63%	176 Missing ⚠️
src/admin/web.ts	45.74%	51 Missing ⚠️
src/admin/crypto.ts	54.83%	14 Missing ⚠️
src/admin/auth.ts	98.30%	1 Missing ⚠️
src/admin/rbac.ts	91.66%	1 Missing ⚠️

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