[Codename-11]

Summary

• make Admin System use Forge's shared build identity instead of the production 1.0.0 fallback
• make the sign-in footer read the packaged application version
• document the canonical version source and add unit plus Postgres-backed router regression coverage

Root cause

instanceAdmin.system read npm_package_version directly. That lifecycle variable is absent in the standalone production runtime, so the router returned its hardcoded 1.0.0 fallback even though package.json and system.buildInfo correctly reported 0.29.7.

Validation

• pnpm vitest run tests/unit/build-info.test.ts
• DATABASE_URL=postgresql://forge:forge@localhost:55432/forge?schema=public REDIS_URL=redis://localhost:56379 pnpm vitest run src/server/routers/__tests__/instance-admin-system.test.ts
• pnpm lint (passes with pre-existing warnings)
• pnpm typecheck
• pnpm docs:build
• git diff --check

Delivery

Implements AXI-154. This PR intentionally contains no version bump, release tag, or deployment change.