flake: update all inputs

[0xda157]

Our lockfiles are getting very out of date (and have been blocking prs). I don't want to wait until #1817 is fixed to keep things update to date.

---

• I certify that I have the right to submit this contribution under the MIT license
• Commit messages adhere to Stylix commit conventions
• Theming changes adhere to the Stylix style guide
• Changes have been tested locally
• Changes have been tested in testbeds
• Each commit in this PR is suitable for backport to the current stable branch

[trueNAHO]

I resolved breaking changes and cherry-picked #1866, which was pending on this nix flake update:

commit 9fd508fc9b38d9b047f501c866cd995cc49add52
Author: awwpotato <awwpotato@voidq.com>
Date:   2025-09-03 22:07:54 -0700

    flake: update all inputs

    Update all inputs, rename the KDE platform, and apply formatter changes
    by running the following commands:

        biome check --unsafe --write
        pre-commit run --all-files

    Rename the KDE platform, following local commit f47c0edcf71e ("treewide:
    remove Plasma 5 support dropped upstream (#1860)") and upstream commits
    [1] ("nixos/treewide: clean up some more references to deleted qt5
    things") and [2] ("qt: deprecate kde6").

    [1]: https://github.com/NixOS/nixpkgs/commit/31d5c4e753c996f5fd431b9988af9db91581ec09
    [2]: https://github.com/nix-community/home-manager/commit/1e759786e526a87a3c05beeff5db41743d763569

    Closes: https://github.com/nix-community/stylix/issues/1865
    Link: https://github.com/nix-community/stylix/pull/1866
    Link: https://github.com/nix-community/stylix/pull/1881

    Reviewed-by: NAHO <90870942+trueNAHO@users.noreply.github.com>
    Co-authored-by: Samuel Meenzen <samuel@meenzen.net>
    Co-authored-by: NAHO <90870942+trueNAHO@users.noreply.github.com>

Interestingly, the "Request Reviewers" GitHub Action works again on this PR for some reason. Maybe it worked because of the force push?

[danth]

Changes LGTM - For clarity it may be better to keep these as separate commits.

[trueNAHO]

Changes LGTM

OK, let's just merge this then.

For clarity it may be better to keep these as separate commits.

This is one atomic breaking change and splitting it up results in partially invalid states:

• - flake: update all inputs          # This is broken without the other two commits.
  - treewide: apply formatter changes
  - qt: rename KDE platform
  

• - treewide: apply formatter changes # This is broken without pulling the formatter changes.
  - qt: rename KDE platform           # This just happens to not crash CI, although it should depend on the updates.
  - flake: update all inputs
  

This is why I put everything into one commit.

[trueNAHO]

CC: @awwpotato, @danth

We should require PRs to be rebased on top of this PR to avoid CI formatting failures once they are merged into master, even if they passed in the PR itself.