Astro garden skeleton: Quartz-compatible URLs, Obsidian markdown, odometer homepage

- glob content loader over the vault's Digital_Garden with verbatim-path ids
- remark plugin: wikilinks, image embeds (wiki + relative md), callouts
- URL parity with live Quartz sitemap verified 102/102 (built set is a
  strict superset: +30 synthetic folder listings)
- KaTeX, lazy mermaid, shiki dual themes, quoted-string draft handling
- copy-assets resolves embeds vault-wide (fixes live-site 404s for
  Blog Scratch/assets images) into flat /assets/
- homepage odometer widget: fetches api.c0smere.net baseline, ticks at
  lifetime average rate, fail-closed hidden on error
- deploy/: nginx try_files config + compose (port 18100) + containerized
  build script for cyrion

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy/nginx.conf

@@ -0,0 +1,23 @@
+server {
+    listen 80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    charset utf-8;
+
+    # Quartz-compatible URLs: /A/B -> A/B.html, /Folder/ -> Folder/index.html
+    location / {
+        try_files $uri $uri.html $uri/index.html =404;
+    }
+
+    location /assets/ {
+        expires 7d;
+        add_header Cache-Control "public";
+    }
+
+    location /_astro/ {
+        # content-hashed filenames — safe to cache hard
+        expires 365d;
+        add_header Cache-Control "public, immutable";
+    }
+}