feat: add Obsidian appearance configuration and update gitignore

- Add `.obsidian/appearance.json` to configure Ubuntu Mono as the default font family
- Remove `.obsidian/appearance.json` and `.obsidian/graph.json` from `.gitignore` to track appearance settings
- Ensure `.vercel` is properly listed in `.gitignore` with a trailing newline

.gitignore

@@ -10,11 +10,9 @@ node_modules
 .cache
 dist
 tmp
-.obsidian/appearance.json
-.obsidian/graph.json
 .obsidian/workspace.json
 .env
 __pycache__
 ansible.cfg
 .vuepress/public/logos
-.vercel
+.vercel

.obsidian/appearance.json

@@ -0,0 +1,5 @@
+{
+  "interfaceFontFamily": "Ubuntu Mono",
+  "textFontFamily": "Ubuntu Mono",
+  "monospaceFontFamily": "Ubuntu Mono"
+}