chore: add copyright headers to web dashboard data modules

[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/dashboard/fixture-health-check.ts
• apps/web/src/dashboard/fixture.ts
• apps/web/src/dashboard/types.ts

[Adeyemi-cmd]

Can i please work on this

[grantfox-oss]

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Next steps:

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