feat: reddit -> spotify/bandcamp artist linker MVP (extension + resolver service)

Firefox MV2 content script that detects artist/band names in reddit comment
threads and rewrites them inline into Spotify + Bandcamp links, backed by a tiny
zero-dependency Node resolver that confirms each candidate against the Spotify Web
API (direct links) or MusicBrainz (zero-setup, search links). Includes build +
install instructions in the README.

Source: project/reddit-spotify-linker (user 2026-06-12) + user message 2026-06-14
"Full vibe code, small service, minimal code."

Closes task/resolver-service, closes task/firefox-extension, closes task/docs-and-publish
(plan/mvp-build, objective/ship-mvp-linker).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,14 @@
+# secrets / local config
+.env
+*.env
+!.env.example
+
+# node
+node_modules/
+npm-debug.log*
+
+# editor / os
+.DS_Store
+*.swp
+.idea/
+.vscode/