[FEATURE] Add panel-level repeat variable support

[adrianSepiol]

Closes: perses/perses#2936

Needs: perses/spec#32

Description

Adds support for repeat panel based on variable. Uses only selected values from dropdown are used.

Screenshots

In below recording you can notice that width of panel is expanded when you select repeat variable and height is used for single tile. If you don't fill 'Max per row' all tiles will be fitted into single row.

Screen.Recording.2026-06-10.at.08.57.13.mov

In this one you can see how the panel will behave when the amount of selected values will change. You can enter edit mode only with first panel.

Screen.Recording.2026-06-10.at.09.00.11.mov

Group repeat has priority over panel repeat.

Screen.Recording.2026-06-01.at.19.14.58.mov

Checklist

• Pull request has a descriptive title and context useful to a reviewer.
• Pull request title follows the [<catalog_entry>] <commit message> naming convention using one of the
  following catalog_entry values: FEATURE, ENHANCEMENT, BUGFIX, BREAKINGCHANGE, DOC,IGNORE.
• All commits have DCO signoffs.

UI Changes

• Changes that impact the UI include screenshots and/or screencasts of the relevant changes.
• Code follows the UI guidelines.
• E2E tests are stable and unlikely to be flaky.
  See e2e docs for more details. Common issues include:
  • Is the data inconsistent? You need to mock API requests.
  • Does the time change? You need to use consistent time values or mock time utilities.
  • Does it have loading states? You need to wait for loading to complete.

[shahrokni]

@adrianSepiol
Could you please check the two following pipelines. It seems they are failing. ci/build and ci/type-check`` And please before that, rebase` with main.

[adrianSepiol]

@adrianSepiol Could you please check the two following pipelines. It seems they are failing. ci/build and ci/type-check And please before that, ``rebase` with main.

@shahrokni Pipelines are failing because of PR mentioned in description that needs to be merged for this to work: perses/spec#32

[adrianSepiol]

Removed "mode" option after comments from @AntoineThebaud in perses/perses#2936. I've updated description of PR.