feat(pwa): derive API base from runtime host by default

[LogenNineFingersIsAlive]

Summary

• resolve PWA API base at runtime from the current browser host when VITE_API_BASE is not configured
• keep explicit VITE_API_BASE override support for custom environments
• update web runtime env injection to avoid forcing a fallback VITE_API_BASE when not configured (while still rewriting when --api-port is explicitly set)

Why

Tailnet/local host changes were causing stale baked API base URLs in the PWA preview bundle, resulting in loading spinners when the API host changed. This makes host selection resilient by default while preserving explicit env control.

Validation

• biome checks for changed files
• pnpm --filter @tithe/tests test -- tests/cli/web.spec.ts
• pnpm --filter @tithe/pwa build

[Copilot]

Pull request overview

Updates the PWA + CLI web runtime so the API base URL is resolved at runtime from the browser host by default (when VITE_API_BASE is not set), avoiding stale baked-in API URLs across host changes while keeping explicit overrides.

Changes:

• PWA: resolve API base URL from window.location when VITE_API_BASE is unset, with normalization for configured values.
• CLI: adjust web runtime env injection so VITE_API_BASE is only injected when explicitly configured or when --api-port is provided.
• Vite preview: allow preview hostnames for localhost and Tailnet (.ts.net).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
apps/pwa/vite.config.ts	Adds preview.allowedHosts to support localhost/Tailnet preview access.
apps/pwa/src/api.ts	Introduces runtime API base URL resolution (env override + browser-host-derived fallback).
apps/cli/src/web.ts	Stops forcing a fallback VITE_API_BASE into the PWA runtime env unless --api-port is set.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.