chore: add copyright headers to web pages

[karagozemin]

Add a per-file copyright header so ownership is visible at the file level (consistent with the root LICENSE).

Mechanical change — prepend this exact line as the first line of each file, nothing else:

// Copyright (c) 2026 Sub Rosa contributors

Add it to the following files:

• apps/web/src/pages/ArchitecturePage.tsx
• apps/web/src/pages/DashboardPage.tsx
• apps/web/src/pages/DemoPage.tsx
• apps/web/src/pages/LandingPage.tsx

[bobo-24]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. I’ll prioritize this immediately and ensure a reliable solution is delivered as soon as possible. Thank you!

[s6pa1rta3n-lab]

I am taking this issue to add the required per-file copyright headers to the four web pages as specified. Opening a PR shortly.