Show XEvents with real product screenshots and a short walkthrough

[ehsan0921]

The README previously had only branding artwork and a screenshot capture plan. This adds actual mobile-size Mini App captures and a 25-second silent walkthrough so visitors can see event creation, RSVP management and code-based group check-in.

• Add seven reviewed product captures, an MP4 and an animated GIF; show four screenshots directly in the README.
• Document capture provenance and boundaries in docs/demo.md. The real frontend and Worker ran against disposable local D1 with fictional identities and events. Telegram launch identity was simulated; all outbound calls were mocked. No production records or credentials were used.
• Create a fictional photography walk through the actual UI and verify an organiser keypad check-in for a two-person group. The guest ticket capture correctly shows the resulting already-checked-in state.

Validation: Worker bundle and mocked local integration checks passed; all 46 changed-document file/image links resolve; whitespace checks passed; heuristic credential-pattern scan covered 606 historical blobs and changed text without matches. Images were visually reviewed; MP4 is H.264, 430 × 932 and 25 seconds, with a frame extracted for verification.

This is a sequence of actual screenshots, not a continuous recording or a live Telegram demonstration. Telegram WebView, chat RSVP, live notifications, QR scanning and payments were not manually verified. No application modules, deployment configuration or production data changed. No deployment or merge performed.