luci-theme-material: fix overview spacing

[owlsy]

Changes

• Resolve mismatched spacing for each heading in their box. This will fix the spacing for when contents are hidden and add spacing when contents are shown. Compliments the hide/show buttons added.

Notes

• Tested on: Safari Version 26.4 (21624.1.16.11.4), OpenWrt 25.12.2 r32802-f505120278 / LuCI openwrt-25.12 branch 26.087.74782~b3f192d
• Could not find PKG_VERSION in the Makefile.
• Large number of code authors, unsure who to select for feedback.
• Part of a collection of pull requests based on luci-theme: Refined CSS for all themes, including adding larger hide/show buttons for smaller screens to all themes #8491

Checklist

• This PR is not from my main or master branch 💩, but a separate branch ✅
• Each commit has a valid ✒️ Signed-off-by: <my@email.address> row (via git commit --signoff)
• Each commit and PR title has a valid 📝 <package name>: title first line subject for packages
• Incremented 🆙 any PKG_VERSION in the Makefile
• Tested on: (architecture, openwrt version, browser) ✅
• ( Preferred ) Mention: @ the original code author for feedback
• ( Preferred ) Screenshot or mp4 of changes:
• Description: (describe the changes proposed in this PR)

[owlsy]

Will need assistance. How do I revert changes from this pull request so it is up to date with master, then apply the requested change again to the file?

Edit: Just going to make a new pull request as I can't remove the latest commit, I had trouble figuring it out without making more of a mess.

[owlsy]

Messed up the commits and couldn't resolve it. Closing and trying again with #8519.

[github-actions]

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Commit 7bf41ca

• ❌ Signed-off-by must match author
  Actual: missing or doesn't match author
  Expected: Signed-off-by: Joshua Criss <owlsy@outlook.com.au>

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