chore: v0.5.0 — bump version + CHANGELOG entry

manifest.json 0.4.0 → 0.5.0. CHANGELOG.md entry documents three
bundled UX improvements:
  - Light mode (Phase 1 auto-follow + Phase 2 manual toggle)
  - Options → Tuner back-link
  - Theme sync across all three surfaces

Zero new permissions, zero new dependencies, zero behaviour change
for existing users (theme defaults to auto = matches v0.4.0 in
dark-OS browsers, which is most installs).

Bundled because v0.4.0 was still in re-review during the work + ship
discipline calls for fewer larger updates over rapid-fire micro-
updates. Same-account re-review window per Web Store rules.

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "RangerHQ Tuner",
-  "version": "0.4.0",
+  "version": "0.5.0",
   "description": "Lightweight SomaFM radio player. Logs what plays. One-click search to Spotify, YouTube, Apple Music, Bandcamp. No telemetry.",
   "author": "David Keane",
   "homepage_url": "https://davidtkeane.com/rangerhq-tuner",