migrate from astro+netlify to tanstack start + self-hosted

Replace the Astro static site with a TanStack Start (Bun runtime) app and
add Dockerfile + compose files so the site can be served from home-main-2
behind the home-reverse-proxy-1 Caddy instead of Netlify. CI workflow
rewritten to build a container image and SSH-deploy to the home host.

.gitignore

@@ -1,7 +1,11 @@
 # build output
 dist/
-# generated types
-.astro/
+.output/
+.nitro/
+.tanstack/
+
+# generated router types
+src/routeTree.gen.ts
 
 # dependencies
 node_modules/
@@ -11,7 +15,7 @@ npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
 pnpm-debug.log*
-
+bun-debug.log*
 
 # environment variables
 .env
@@ -22,3 +26,6 @@ pnpm-debug.log*
 
 # jetbrains setting folder
 .idea/
+
+# editor
+.vscode/