Feature Policies API + Invitations Policies (#375)

- Added Feature Policy API: a declarative system to enable/disable/modify default behavior in the SaaS kit
- Team invitation policies with pre-checks using the Feature Policy API: Invite Members dialog now shows loading, errors, and clear reasons when invitations are blocked
- Version bump to 2.16.0 and widespread dependency updates (Supabase, React types, react-i18next, etc.).
- Added comprehensive docs for the new policy system and orchestrators.
- Subscription cancellations now trigger immediate invoicing explicitly

apps/e2e/tests/invitations/invitations.po.ts

@@ -115,18 +115,17 @@ export class InvitationsPageObject {
   async acceptInvitation() {
     console.log('Accepting invitation...');
 
-    const click = this.page
-      .locator('[data-test="join-team-form"] button[type="submit"]')
-      .click();
-
-    const response = this.page.waitForResponse((response) => {
-      return (
-        response.url().includes('/join') &&
-        response.request().method() === 'POST'
-      );
-    });
-
-    await Promise.all([click, response]);
+    await Promise.all([
+      this.page
+        .locator('[data-test="join-team-form"] button[type="submit"]')
+        .click(),
+      this.page.waitForResponse((response) => {
+        return (
+          response.url().includes('/join') &&
+          response.request().method() === 'POST'
+        );
+      }),
+    ]);
 
     console.log('Invitation accepted');
   }