perf: self-host fonts and add /admin route

Self-hosted fonts:
- Download all 10 typefaces (35 font files, 728KB) from Google Fonts
- Create @font-face declarations in assets/css/fonts.css
- Remove Google Fonts external dependency from layouts
- Privacy improvement (no Google tracking)
- Performance improvement (no DNS lookup to fonts.googleapis.com)
- GDPR compliant (no third-party requests)

Admin access:
- Add /admin route that redirects to /admin/theme (requires auth)
- Remove Admin link from footer (too visible for visitors)
- Shop owners can bookmark or type /admin directly

Layout improvements:
- Create shop_root.html.heex as minimal root for shop pages
- Shop pages no longer show admin nav bar

Other:
- Update .gitignore to exclude digested static files
- Add PageSpeed 100% task to ROADMAP.md
- Fix test to check /users/settings instead of shop homepage

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ROADMAP.md

@@ -339,7 +339,30 @@ This ensures sellers never unknowingly sell at a loss due to Printify price chan
 
 ## Quick Wins (Low Effort)
 
-*(None pending)*
+### PageSpeed 100% Score
+**Status:** In progress
+**Effort:** 0.5-1 day
+
+Achieve 100% Google PageSpeed score on all core metrics.
+
+**Completed:**
+- [x] Self-hosted fonts (removed Google Fonts external dependency)
+- [x] Production asset pipeline (minified, gzipped CSS/JS)
+
+**Remaining:**
+- [ ] Add proper image dimensions to all `<img>` tags (CLS)
+- [ ] Preload critical fonts (LCP)
+- [ ] Lazy load below-fold images
+- [ ] Add `fetchpriority="high"` to hero images
+- [ ] Optimise mockup images (resize to actual display sizes, WebP format)
+- [ ] Review and reduce unused CSS (currently 22KB gzipped)
+- [ ] Add cache headers for static assets
+
+**Metrics to hit:**
+- Performance: 100
+- Accessibility: 100
+- Best Practices: 100
+- SEO: 100
 
 ---
 
@@ -480,3 +503,14 @@ The project is currently named `simpleshop_theme` (reflecting its origins as a t
 - Shadow above nav for visual separation
 - Hidden on desktop (≥768px), replaces header nav on mobile
 - Works in both live shop and theme preview modes
+
+### Self-Hosted Fonts ✅
+- Removed Google Fonts external dependency
+- All 10 typefaces (35 font files, 728KB) served from `/fonts/`
+- Privacy improvement (no Google tracking)
+- Performance improvement (no DNS lookup to fonts.googleapis.com)
+- GDPR compliant (no third-party requests)
+
+### Admin Access Route ✅
+- `/admin` redirects to `/admin/theme` (requires auth)
+- Shop owners can bookmark or type `/admin` to access