Game share-loop: instrument funnel, deep-link shares, /play metadata

Sharpen the existing daily-game share loop into something measurable (per Codex's
"instrument what you have, then feed people into it" plan), ahead of a Show HN launch.

Analytics:
- Per-game funnel events <game>_{arrival,started,completed,shared} (article_id=0).
  arrival = landed via a shared link (utm_source=game_share); started = first move
  (guess/find/flip); completed = solved/cleared/Full Bloom; shared = on share success.
- trackVisit() moved into the global layout so direct /play landings count; the
  server-rendered /a/ share page now creates a visitor token + sends a daily visit
  beacon (first-time /a/-only visitors were previously dropped).
- Admin "Games funnel" panel: arrivals / engaged / completed / shared, per game.

Sharing:
- Memory Match gains a Share button (it was the only game without one).
- All shares deep-link to the exact game+variant with a full https:// URL +
  utm_source=game_share (gameShareUrl helper), instead of a bare /play.
- "shared" is counted only after navigator.share()/clipboard.writeText() succeeds.

/play social metadata:
- /play served homepage canonical/OG (static SPA, ssr=false). postbuild script
  patches build/play.html's head to /play canonical/title/description/OG; fails the
  build if the homepage tags drift. Caddy try_files now serves {path}.html so /play
  is served from the patched file (snapshot in deploy/caddy/).

Tests: backend 352, frontend 27.

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

frontend/src/lib/components/BloomGame.svelte

@@ -1,6 +1,7 @@
 <script>
   import { getJSON, postJSON } from '$lib/api.js';
   import { pushGameState, fetchGameStats } from '$lib/gamesync.js';
+  import { trackGame, gameShareUrl } from '$lib/analytics.js';
 
   // mode: 'daily' (shared, synced, ritual) | 'free' (local-only, infinite wheels)
   // format: 'center' (center letter required) | 'wild' (any word from the 7)
@@ -208,13 +209,14 @@
       return;
     }
     const pan = isPangram(w);
+    if (found.length === 0) trackGame('bloom', 'started');   // first word = started
     found = [w, ...found];
     flash(pan ? 'Pangram! 🌸 +' + scoreWord(w) : '+' + scoreWord(w));
     if (pan) bloomPulse();
     persist();
     if (!isFree) syncSoon();
     if (found.reduce((s, x) => s + scoreWord(x), 0) >= maxScore && !fullShown) {
-      fullShown = true; bloomPulse();
+      fullShown = true; bloomPulse(); trackGame('bloom', 'completed');   // Full Bloom
     }
   }
 
@@ -225,9 +227,10 @@
     found.forEach((w) => (byLen[w.length] = (byLen[w.length] || 0) + 1));
     const breakdown = Object.keys(byLen).sort((a, b) => b - a).map((l) => `${l}×${byLen[l]}`).join('  ');
     const pang = found.some(isPangram) ? ' · pangram ✓' : '';
-    const text = `Upbeat Bytes · Bloom ${date}\n${fullBloom ? 'Full Bloom 🌸' : tier.name} · ${found.length} words${pang}\n${breakdown}\nupbeatbytes.com/play`;
-    if (navigator.share) navigator.share({ text }).catch(() => {});
-    else navigator.clipboard?.writeText(text).then(() => { copied = true; setTimeout(() => (copied = false), 1500); });
+    const bloomV = mode === 'daily' ? 'daily' : (format === 'wild' ? 'free-wild' : 'free-center');
+    const text = `Upbeat Bytes · Bloom ${date}\n${fullBloom ? 'Full Bloom 🌸' : tier.name} · ${found.length} words${pang}\n${breakdown}\n${gameShareUrl('bloom', bloomV)}`;
+    if (navigator.share) navigator.share({ text }).then(() => trackGame('bloom', 'shared')).catch(() => {});
+    else navigator.clipboard?.writeText(text).then(() => { trackGame('bloom', 'shared'); copied = true; setTimeout(() => (copied = false), 1500); });
   }
 
   // Quiet "this should count?" — flags a rejected word for the admin queue.