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/v0.2.108.ts

@@ -0,0 +1,13 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_108 = VersionInfo.of({
+  version: '0.2.108:0',
+  releaseNotes: {
+    en_US:
+      "Settings panel CTA fixes for tenants. (1) The 'Upgrade to Pro' pill on the Plan section now reads 'Upgrade' for free signed-in users and trial visitors — clicking opens the buy modal showing Pro and Max side-by-side, so labeling the pill 'Upgrade to Pro' was misleading (you're not committing to Pro by clicking, you're opening a comparison). Pro users (not Max) see 'Upgrade to Max' since the destination is unambiguous — clicking pre-selects the Max tier in the buy modal. (2) The 'Sign up' button on the Account section (anon trial + not-signed-in states) now opens the 3-tier signup modal (Free / Pro / Max) instead of dropping the visitor on the magic-link form. Same modal as the toolbar 'Sign up' pill — visitors get the full pricing menu before committing to a tier. Both fixes apply on mobile and web (the settings panel renders the same on both)."
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})