Design pass: fix dead site config, add hero image support, polish cards

- Fix applyConfig self-recursion (const _origApply captured the hoisted
  wrapper itself): site.json config — theme, portfolio, socials, bio —
  was never applied; site silently fell back to hardcoded brown defaults
- Strengthen theme test to assert the configured primary color exactly
- Portfolio covers: styled placeholder on missing image (like locations),
  restore img when Immich carousel kicks in; overlay always visible on touch
- Optional hero photo via site.heroImage with soft scrim (activates only
  when the image loads); site.json points at /images/hero.jpg
- Option cards: equal height, centered content
- /#book deep link also works via hashchange

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

config/site.json

@@ -4,7 +4,8 @@
     "tagline": "Capturing life's beautiful moments",
     "description": "Senior portraits, engagement sessions, and milestone photography",
     "logo": "/images/logo.png",
-    "favicon": "/images/favicon.ico"
+    "favicon": "/images/favicon.ico",
+    "heroImage": "/images/hero.jpg"
   },
   "photographer": {
     "name": "Elysse Hodgkin",