refactor: remove lite variant, fix release workflow

- Remove all lite/full variant logic from frontend, API, shared constants,
  docs, and tests (single unified Docker image only)
- Replace single QEMU multi-arch Docker build with per-architecture native
  builds (amd64 + arm64) and manifest merge to fix disk space exhaustion
- Add disk cleanup step and per-platform build cache scopes
- Switch release trigger from push to workflow_dispatch
- Add GitHub issue templates and PR template

tests/e2e/people.spec.ts

@@ -1,7 +1,7 @@
 import { test as base, expect } from "@playwright/test";
 import { test as uiTest } from "./helpers";
 
-const API = "http://localhost:13490";
+const API = process.env.API_URL || "http://localhost:13490";
 
 async function getAuthToken(): Promise<string> {
   const res = await fetch(`${API}/api/auth/login`, {