[azure-keyvault-exporter] bump app to 26.1.0

[sturman]

What this PR does / why we need it

Bumps the default azure-keyvault-exporter image from 24.9.1 to the latest release 26.1.0, and bumps the chart version 1.0.12 → 1.1.0.

This supersedes #105 (Renovate), whose lint, install check fails because it only changes appVersion. ct lint rejects that with chart version not ok. Needs a version bump!.

Which issue this PR fixes

• supersedes Update webdevops/azure-keyvault-exporter Docker tag to v26 #105

Special notes for your reviewer

Upstream changes between 24.9.1 and 26.1.0 that users should know about:

• Logger flags changed (slog migration, 25.12.0). --log.debug / --log.devel / --log.json (LOG_DEBUG / LOG_DEVEL / LOG_JSON) were replaced by --log.level, --log.format, --log.source, --log.color and --log.time. Passing an old flag through custom args now fails at startup with unknown flag; the old env vars are ignored. The chart itself doesn't set any of these, so the templates didn't need changes.
• Log output format changed (zap → slog JSON).
• Built with Go 1.25.6, and arm64 images ship an arm64 binary again (fixed in 26.1.0).
• No changes to metric names or labels.

Tested locally:

• ct lint --config ct.yaml passes, including the version increment check.
• helm install --wait on kind with ci/env-values.yaml and ci/secret-values.yaml passes; the pod becomes ready with docker.io/webdevops/azure-keyvault-exporter:26.1.0.

Checklist

• Chart Version bumped
• Title of the PR starts with chart name (e.g. [azure-metrics-exporter])