Fix non-ASCII hyphens in commitlint config & add merge commit skip rule

[coderabbitai]

Issue Description

The current commitlint configuration file contains non-ASCII hyphens in the ignore rules which may not match actual commit messages correctly:

// In current commitlint.config.mjs
(message) => message.includes('Signed‑off‑by: dependabot[bot]'),

Proposed Changes

1. Replace non-ASCII hyphens with ASCII hyphens to ensure proper matching:

   (message) => message.includes('Signed-off-by: dependabot[bot]'),

2. Add an additional ignore rule for merge commits:

   // skip merge commits generated by GitHub/Git
   (message) => message.startsWith('Merge '),

References

• Discussion started in PR: feat: add multi-stage Dockerfile for building and running app #342 (comment)