feat(dev): proxy /pb to PocketBase in ng serve

Add proxy.conf.mjs mirroring `location /pb/` from nginx: the prefix is
stripped, target comes from PB_URL (empty value falls back to the default,
same as the SSR provider). Cover the config with tests in tests/lint and
update docs.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/lint/pb-dev-proxy.spec.ts

@@ -0,0 +1,36 @@
+// Проверяет правило `/pb/` в proxy.conf.mjs: оно должно повторять `location /pb/` из nginx и серверный `PB_URL`.
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+type Rules = typeof import('../../proxy.conf.mjs').default;
+
+async function loadRules(pbUrl: string | undefined): Promise<Rules> {
+    vi.stubEnv('PB_URL', pbUrl);
+    vi.resetModules();
+    return (await import('../../proxy.conf.mjs')).default;
+}
+
+describe('прокси /pb для ng serve', () => {
+    afterEach(() => vi.unstubAllEnvs());
+
+    it('содержит правило /pb/ с target из PB_URL', async () => {
+        const rules = await loadRules('http://pb.test:1234');
+
+        expect(rules['/pb/']?.target).toBe('http://pb.test:1234');
+        expect(rules['/pb/']?.changeOrigin).toBe(true);
+    });
+
+    it.each([undefined, ''])('при PB_URL=%j target — http://127.0.0.1:8090', async (pbUrl) => {
+        const rules = await loadRules(pbUrl);
+
+        expect(rules['/pb/']?.target).toBe('http://127.0.0.1:8090');
+    });
+
+    it('rewrite срезает префикс /pb', async () => {
+        const rewrite = (await loadRules(undefined))['/pb/']?.rewrite;
+
+        expect(rewrite?.('/pb/api/health')).toBe('/api/health');
+        expect(rewrite?.('/pb/api/collections/x/records?a=1')).toBe(
+            '/api/collections/x/records?a=1',
+        );
+    });
+});