Add multi-tenant cloud mode: self-serve purchase, credit metering, core-decoupling

Introduces RECAP_MODE=multi alongside single-mode self-host:
- Tenant auth + accounts (magic-link via System SMTP), per-tenant credit pool,
  anonymous trial minting with per-IP/-64 caps
- Self-serve Pro/Max purchase: inline Lightning (BTCPay) + card (Zaprite),
  prepaid 30-day periods, expiry-reminder emails
- Core-decoupling: relay owns cloud tier/expiry keyed by Recaps user-id
- SQLite (better-sqlite3) schema for multi-mode; filesystem unchanged for single
- StartOS actions/versions through 0.2.155

public/manifest.json

@@ -0,0 +1,32 @@
+{
+  "name": "Recap",
+  "short_name": "Recap",
+  "description": "Summarize YouTube videos and podcasts. Paste a link, get topic-level summaries with timestamps.",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "any",
+  "background_color": "#0a0e1a",
+  "theme_color": "#0a0e1a",
+  "icons": [
+    {
+      "src": "/assets/icon.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/assets/icon.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/assets/icon.png",
+      "sizes": "1024x1024",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ],
+  "categories": ["productivity", "utilities"]
+}