chore(renovate): add dashboard, lockfile maintenance and pub rules

[TheMeinerLP]

Proposed changes

New in renovate.json:

• dependencyDashboard — one issue listing everything pending.
• lockFileMaintenance — refreshes pubspec.lock weekly (Monday before 5am).
• rangeStrategy: bump for pub — pubspec.yaml pins caret ranges, so Renovate's default replace strategy never fires for an in-range update and Dart dependencies silently went stale.
• Dart minor updates grouped into a single automerged PR.

Changed: the custom manager for chart templates now keys off an explicit # renovate: marker instead of matching every image: name:tag line it can find.

# charts/stelaris-ui/templates/tests/test-connection.yaml
- name: check
  # renovate: datasource=docker depName=curlimages/curl
  image: curlimages/curl:8.20.1

The reason for the marker: the chart's own image line is image: {{ include "stelaris-ui.image" . }} and carries no version at all — the tag comes from appVersion via _helpers.tpl. So the only thing this manager can ever match is a third-party image, and saying so explicitly keeps it from matching something it shouldn't later on.

On the chart's own image

An earlier draft of this change pinned image.tag in values.yaml to a fixed version with a Renovate marker on it. That is deliberately not part of this PR: tag: "" falls back to .Chart.AppVersion (_helpers.tpl:57), Chart.yaml documents that coupling, and tests/deployment_test.yaml:113 asserts it. Pinning the tag would break that test and let the chart version and the image version drift apart. The image is built by this repo and released by release-please — it is not a dependency Renovate should be tracking.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply) — CI configuration

Checklist

• I have read the CONTRIBUTING.md
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

Verified locally:

• Every customManager regex was run against the real files it targets. All three match what they should: flutter = 3.47.1 (Dockerfile + build_pr.yml), curlimages/curl = 8.20.1 (chart template, datasource from the marker), helm-unittest/helm-unittest = v1.1.2 (build_pr.yml). No manager comes back empty.
• helm lint clean, helm unittest 18/18 passing, and helm template still renders harbor.onelitefeather.dev/onelitefeather/stelaris:1.3.0 from appVersion.

One note: matchUpdateTypes: [patch] → automerge: true is carried over unchanged, but the central preset (:default(...)) already enables patch automerge. It is redundant rather than wrong — happy to drop it if you'd rather keep the config minimal.

🤖 Generated with Claude Code