feat: add @bchen/ui v0.1.0 — dark-mode token palette and 16px base rule

- dist/tokens.css: canonical light + @media dark semantic-token palette
  extracted from inventory (cross-checked against authd and buchinese).
  Covers --fg, --fg-muted, --bg, --bg-elevated, --surface, --accent*,
  --danger*, --border*, --input-*, --warning, primitive --gray-* scale.
- dist/base.css: `input, textarea, select { font-size: 16px; }` prevents
  iOS Safari auto-zoom on focus.
- tests/tokens.test.ts: vitest — token presence in both light and dark
  blocks; WCAG AA contrast (>=4.5:1 body, >=3.0:1 UI) via inline
  hex-to-luminance math. All 10 tests green.
- tests/base.test.ts: vitest — asserts 16px rule covers all three selectors.
- .gitea/workflows/release.yml: tag-triggered CI — npm ci + npm test,
  CHANGELOG version gate, dist/scripts security grep, Gitea release
  artifact upload.
- README.md: four-step consumer integration guide with copy-pasteable
  snippets (package.json dep, Dockerfile cp, HTML link tags, app CSS).
- CHANGELOG.md: v0.1.0 entry.

npm audit --omit=dev: 0 vulnerabilities

Closes #1

CHANGELOG.md

@@ -0,0 +1,11 @@
+# Changelog
+
+All notable changes to `@bchen/ui` will be documented in this file.
+
+## [0.1.0] — 2026-05-13
+
+### Added
+
+- `dist/tokens.css` — canonical dark-mode semantic-token palette for the bchen.dev fleet. Light-mode `:root` block with primitive palette (`--black`, `--white`, `--gray-*`, `--red`) and semantic tokens (`--fg`, `--fg-muted`, `--bg`, `--bg-elevated`, `--surface`, `--accent`, `--accent-fg`, `--accent-hover`, `--danger`, `--danger-fg`, `--danger-bg`, `--warning`, `--border-color`, `--border-strong`, `--border`, `--input-*`). `@media (prefers-color-scheme: dark)` block overrides all color-sensitive tokens for OS-driven dark mode.
+- `dist/base.css` — `input, textarea, select { font-size: 16px; }` rule. Prevents iOS Safari auto-zoom on focus (requires computed font-size ≥ 16px).
+- WCAG AA contrast tested in CI: `--fg/--bg` and `--fg-muted/--bg` ≥ 4.5:1, `--border-strong/--bg` ≥ 3.0:1, in both light and dark.