refactor: purge Node.js, Rust is the one true backend

- Moved boosapi-rs/* to repo root
- Deleted all Node.js source (src/server/, src/web/, scripts/)
- Deleted node_modules, package.json, tsconfig, vite.config
- Updated .gitignore and AGENTS.md for Rust-only stack
- Fixed static file path for frontend dist/web/
- Dockerfile stays the same (already Rust-only)
- Kept dist/web/ for Rust static serving

src/web/pages/accounts.centered-modal.test.ts

@@ -1,15 +0,0 @@
-import { describe, expect, it } from 'vitest';
-import { readFileSync } from 'node:fs';
-import { resolve } from 'node:path';
-
-describe('Accounts centered modal adoption', () => {
-  it('uses CenteredModal for add/edit/rebind flows instead of inline panel cards', () => {
-    const source = readFileSync(resolve(process.cwd(), 'src/web/pages/Accounts.tsx'), 'utf8');
-
-    expect(source).toContain(
-      'import CenteredModal from "../components/CenteredModal.js";',
-    );
-    expect(source).toContain('<CenteredModal');
-    expect(source).not.toContain('className={`card panel-presence rebind-panel');
-  });
-});