Switch homepage review stat from Facebook to Google

- Replace inc/facebook-stats.php with inc/google-reviews.php: fetches
  average star rating + review count from the Places API (New) instead
  of Facebook's Graph API, same cache-to-JSON/fallback-on-failure shape
  as before.
- index.php: stat card now shows the native star rating ("4.8★ average
  rating") instead of a recommend %, sourced from Google. Drops the
  Facebook-followers line entirely — Google's API has no equivalent and
  showing a stale/static number wasn't worth keeping. "Follow on
  Facebook" links elsewhere on the site are untouched.
- config.example.php: swap FB_PAGE_ID/FB_PAGE_ACCESS_TOKEN/
  FB_STATS_CACHE_TTL/FB_FALLBACK_* for GOOGLE_PLACE_ID/
  GOOGLE_PLACES_API_KEY/GOOGLE_STATS_CACHE_TTL/GOOGLE_FALLBACK_RATING/
  GOOGLE_FALLBACK_REVIEW_COUNT (set to the pub's actual 4.8★/71 reviews),
  with setup instructions in comments. config.php (gitignored) updated
  to match.
- Remove the now-dead .stat-row CSS that only existed for the dropped
  followers line; rebuild styles.css.

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

src/scss/styles.scss

@@ -665,16 +665,6 @@
     color: var(--ink-muted);
   }
 
-  .stat-card .stat-row {
-    margin-top: 1.5rem;
-    padding-top: 1.5rem;
-    border-top: 1px solid var(--rule);
-  }
-
-  .stat-card .stat-row .stat-big {
-    font-size: 1.9rem;
-  }
-
   .stat-source {
     margin-top: 1.5rem;
     font-family: var(--font-mono);