MAINT: Update package minimum versions

[VeckoTheGecko]

Description

Update package minimum versions according to SPEC0.

Run

uvx --from xarray-minimum-dependency-policy==2.0.0 \
          minimum-versions validate \
          --policy=.github/ci/policy.yaml \
          --manifest-path=./pixi.toml \
          pixi:test-minimum

Before:

After

Checklist

• Closes None
• Tests added
• This PR targets the correct branch (main for normal development, v3-support for v3 support)

AI Disclosure

None used

[VeckoTheGecko]

With this PR adding copernicusmarine now works @erikvansebille

[VeckoTheGecko]

(easier to review commit by commit)

[erikvansebille]

Looks good and indeed I can now pixi add copernicusmarine locally; happy to be merged!