Add Activepieces integration for workflow automation

- Add Activepieces fork with SmoothSchedule custom piece
- Create integrations app with Activepieces service layer
- Add embed token endpoint for iframe integration
- Create Automations page with embedded workflow builder
- Add sidebar visibility fix for embed mode
- Add list inactive customers endpoint to Public API
- Include SmoothSchedule triggers: event created/updated/cancelled
- Include SmoothSchedule actions: create/update/cancel events, list resources/services/customers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

activepieces-fork/docs/build-pieces/building-pieces/piece-authentication.mdx

@@ -0,0 +1,38 @@
+---
+title: 'Add Piece Authentication'
+icon: 'circle-4'
+description: ''
+---
+
+
+### Piece Authentication
+
+Activepieces supports multiple forms of authentication, you can check those forms [here](../piece-reference/authentication)
+
+Now, let's establish authentication for this piece, which necessitates the inclusion of an API Key in the headers.
+
+Modify `src/index.ts` file to add authentication,
+
+```ts
+import { PieceAuth, createPiece } from '@activepieces/pieces-framework';
+
+export const gelatoAuth = PieceAuth.SecretText({
+  displayName: 'API Key',
+  required: true,
+  description: 'Please use **test-key** as value for API Key',
+});
+
+export const gelato = createPiece({
+  displayName: 'Gelato',
+  logoUrl: 'https://cdn.activepieces.com/pieces/gelato.png',
+  auth: gelatoAuth,
+  authors: [],
+  actions: [],
+  triggers: [],
+});
+```
+
+<Note>
+  Use the value **test-key** as the API key when testing actions or triggers for
+  Gelato.
+</Note>