chore: v0.5.1 — bump version + CHANGELOG entry

manifest.json 0.5.0 → 0.5.1. CHANGELOG.md entry for the
Quick Stations 8 → 14 expansion (merged from v0.5.1-prep,
commit 609e0ed).

Tagged on Gitea but NOT uploaded to Chrome Web Store until
v0.5.0 clears re-review. Per David: 'we will ship to web store
after the last one gets accepted, that one is important so a
user knows what to do' — the v0.5.0 first-run hint + light
mode + theme toggle are higher-value features and should land
in users' browsers before this stations expansion piles on top.

manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "RangerHQ Tuner",
-  "version": "0.5.0",
+  "version": "0.5.1",
   "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",