feat(analytics): retire Rybbit and add SEO/GEO discovery tracking

Document Umami as the sole analytics platform, remove Rybbit proxy and
tracker code, and classify public page traffic with discovery_channel for
adm SEO/GEO dashboards.

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

@@ -18,8 +18,7 @@ H5_PORT=8081
 # pnpm dev / dev-core 在未显式覆盖时会把 H5_PUBLIC_BASE_URL 设为 8081。
 H5_PUBLIC_BASE_URL=http://127.0.0.1:5173
 
-# Local Umami analytics (disabled by default; points only to the local
-# memind-analytics service when enabled).
+# 访问统计平台说明（Umami 唯一；Rybbit 已退役 2026-08）见 docs/analytics-platform.md
 # MEMIND_ANALYTICS_ENABLED=true
 # MEMIND_ANALYTICS_URL=http://127.0.0.1:3100
 # MEMIND_ANALYTICS_WEBSITE_ID=<local Umami Website ID>
@@ -30,12 +29,7 @@ H5_PUBLIC_BASE_URL=http://127.0.0.1:5173
 # MEMIND_PRODUCT_ANALYTICS_ENABLED=true
 # MEMIND_PRODUCT_ANALYTICS_WEBSITE_ID=<local Umami product Website ID>
 
-# Local Rybbit analytics (same-origin /rybbit proxy to rybbit.tkmind.cn).
-# Create a Rybbit Site for localhost / 127.0.0.1, then set its numeric site_id.
-# MEMIND_RYBBIT_ENABLED=true
-# MEMIND_RYBBIT_URL=https://rybbit.tkmind.cn
-# MEMIND_RYBBIT_SITE_ID=<numeric site id>
-# MEMIND_RYBBIT_ID_SECRET=<local-only pseudonymization secret>
+# 访问统计仅使用 Umami；Rybbit 已退役，见 docs/analytics-platform.md
 
 # 生产 H5 public base 当前临时切到 https://mm.tkmind.cn。
 # 后续公网 H5 不再依赖 105 转发链路；m.tkmind.cn 仅作为 legacy/rollback 记录处理。