Add reworked v13 health check dashboard

[avandras]

Description

This is a greatly reorganized version of the 0. Health check dashboard. The following changes were done:

• use rows for ordering the different panels into thematic groups
• add text panels for further grouping (unfortunately, Grafana has a somewhat limited toolset for ordering stuff semantically)
• unify base colour for all panels, remove default gradient to obtain a less dizzying look :)
• adjust other threshold colours, too (might need further adjustment)
• check all queries and adjust them where necessary
• rename some panels to be more concise/easier to understand
• rewrite some descriptions to be more to the point in some cases (probably a lot more is needed)

AI & Automation Policy

• I am the human author and take full personal responsibility for every change in this PR.
• No AI or automated generative tool was used in any part of this PR OR I have disclosed all tool(s) below.

AI/automation tools used (leave blank if none):

Checklist

• Code compiles and existing tests pass locally.
• New or updated tests are included where applicable.
• Documentation is updated where applicable.

[coveralls]

Coverage Report for CI Build 27813095106

Coverage decreased (-0.07%) to 85.746%

Details

• Coverage decreased (-0.07%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 4 coverage regressions across 1 file.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

4 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
internal/reaper/reaper.go	4	52.79%

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Coverage Stats

Relevant Lines:	5451
Covered Lines:	4674
Line Coverage:	85.75%
Coverage Strength:	0.98 hits per line

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💛 - Coveralls

[avandras]

A small note: apparently starting from Grafana 12.4, the values of small panels (like the stats panels here) are compressed by some unneeded padding of the respective div elements. This can be circumvented by adding the following to[feature_toggles] in grafana.ini :

newPanelPadding = false

The result will look like (except the colours have been changed somewhere during the screenshotting)