feat(secrets-mcp): public home at /, login at /login (0.2.2)

Bump secrets-mcp to 0.2.2 and sync Cargo.lock.

Add home.html landing with SEO and footer link to the refining/secrets
repository; serve it at / and expose /login for sign-in.

Update OAuth error redirects and dashboard unauthenticated redirects to
/login. Improve login page meta tags, back-home link, and OAuth error
alert. Refresh llms.txt and robots.txt.

Made-with: Cursor

crates/secrets-mcp/static/robots.txt

@@ -8,8 +8,11 @@ Disallow: /api/
 Disallow: /dashboard
 Disallow: /audit
 Disallow: /auth/
+Disallow: /login
 Disallow: /account/
 
+# 首页 `/` 为公开安全说明页，允许抓取。
+
 # 面向 AI / LLM 的机器可读站点说明（Markdown）：/llms.txt
 # Human & AI-readable site summary: /llms.txt (also /ai.txt)
 
@@ -24,4 +27,5 @@ Disallow: /api/
 Disallow: /dashboard
 Disallow: /audit
 Disallow: /auth/
+Disallow: /login
 Disallow: /account/