Migrate Liminal Notes CI and devcontainers to shared org image family

[ScottMorris]

Migrate Liminal Notes CI image usage and devcontainer configuration to the shared org image family.

Scope

• Replace *-ci-base-{desktop,android,test} references with shared CI images from .github.
• Switch Liminal Notes devcontainers to the new shared dev images from .github instead of carrying repo-local container behaviour where a shared image should own it.
• Use additive repo-specific layers only where they are genuinely required.
• Retire per-repo image publication after transition stability.

Acceptance Criteria

• test-ci, desktop publish, and Android build workflows pass with shared CI images.
• Liminal Notes devcontainers open successfully against the shared dev image family.
• Repo-local devcontainer workarounds are removed or reduced to genuinely repo-specific settings.
• Legacy per-repo image workflow is retired or archived after the stability window.