chore: Bump copyright headers to 2026

[knst]

What was done?

Annual copyright bump for headers of files

previous year: #6546

How Has This Been Tested?

N/A

Breaking Changes

N/A

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation
• I have assigned this pull request to a milestone (for repository code-owners and collaborators only)

[github-actions]

⚠️ Potential Merge Conflicts Detected

This PR has potential conflicts with the following open PRs:

• refactor: consolidate Dash-specific utils between C++23 polyfills (util/std23.h) and helpers (util/helpers.h) #7098 - refactor: consolidate Dash-specific utils between C++23 polyfills (util/std23.h) and helpers (util/helpers.h)
• feat!: migrate additional indexes from synchronous to async operation #7101 - feat!: migrate additional indexes from synchronous to async operation

Please coordinate with the authors of these PRs to avoid merge conflicts.

[UdjinM6]

For this scripted-diff to work you need to set commit date to 2025 4505e31 and we have to change our linters workflow to fetch full git history 6ca41ff (fetching it after this patch takes 30s vs 4s in develop).
CI: https://github.com/UdjinM6/dash/actions/runs/20700746680/job/59422611796

[knst]

fetching it after this patch takes 30s vs 4s in develop).

I force-pushed non-scripted diff. As far as I remember it hadn't worked correctly in previous years too by some other reasons (output never match with my localhost)

2024 is not scripted (by pasta): 832443a
2023 is not scripted (by me): 097a8e7
2023 is not scripted (by udjin): 498e8c5

[UdjinM6]

utACK 3f12940

(consider docs -> chore here too)

[github-actions]

This pull request has conflicts, please rebase.

[UdjinM6]

utACK eb5c1b8

[kwvg]

utACK eb5c1b8