The ci-base container ships an older Node.js where undici's dependency
on the global File API fails. Passing --bun to bunx runs web-ext through
bun's runtime, avoiding the stale system node entirely.
Replace npx with bunx in Makefile targets and drop setup-node steps
from CI workflows (ci-base container provides bun). Also fix web-ext
lint issues by adding browser_specific_settings.gecko with an extension
ID and data_collection_permissions to the manifest.
Replace Woodpecker CI with GitHub/Forgejo Actions workflows matching
the patterns used in mattermost-marketplace-ng. Add CI workflow with
lint and build jobs, and release workflow with artifact upload.
Also update .gitignore with web-ext-artifacts and AI tool entries.