chore(release): bump version to 0.3.0

[RyleaStark]

Summary

Final release layer for the lnSwitchboard dependency and release-readiness stack.

• bumps VERSION from 0.2.3 to 0.3.0
• updates the pinned Compose image from 0.2.3 to 0.3.0
• leaves the application, dependency, security, container, and publication hardening in the preceding stack layers

Stack

1. chore(deps): refresh frontend dependencies #1 — frontend dependency and security refresh
2. chore(deps): refresh backend dependencies #2 — backend runtime dependency refresh
3. ci(deps): automate dependency maintenance #3 — dependency automation, security gates, immutable Actions, and pinned toolchains
4. chore: harden minor release readiness #5 — application, container, documentation, and release-readiness audit/fixes
5. This PR — version bump and multi-architecture publication trigger

Depends on #5 and must remain the top layer of stack #4.

Release behavior

This pull request does not publish images while running on the PR ref. Once the stack is reviewed and merged to main, the release workflow will:

1. require the version increase from 0.2.3 to 0.3.0;
2. build the verified linux/amd64 and linux/arm64 release image;
3. publish immutable 0.3.0 tags to GHCR and Docker Hub;
4. verify shared digests, architectures, and OCI version/revision labels;
5. promote the verified release to latest in both registries;
6. verify the final version and latest tags across both registries.

Partial cross-registry publication is resumable without overwriting an existing version tag.

Verification

• actionlint 1.7.12
• docker compose config --quiet
• semantic-version assertion: 0.3.0 > 0.2.3
• Compose image assertion: ghcr.io/ryleastark/lnswitchboard:0.3.0
• git diff --check
• confirmed the 0.3.0 version tag is currently unpublished in GHCR and Docker Hub

The preceding readiness layer is green for backend, frontend, and multi-architecture container checks.