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

startos/versions/v0.2.86.ts

@@ -0,0 +1,12 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_86 = VersionInfo.of({
+  version: '0.2.86:0',
+  releaseNotes: {
+    en_US: 'Fountain (fountain.fm) podcast links now work. Paste any fountain.fm/episode/<id> link and Recap fetches the page\'s Open Graph metadata to pull the direct MP3 URL, podcast + episode title, upload date, and duration — no API key, no PodcastIndex lookup needed. Title parsing splits the podcast name from the episode name on Fountain\'s "Show • Episode • Watch on Fountain" format. Smoke-tested against the Rabbit Hole Recap #408 episode. Added Fountain to the "What can I recap?" popover so visitors know it\'s supported.',
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})