chore(release): bump version to 1.2.8 "My QBZ"

Mixtapes & Collections release. Bumps all version references
(Cargo.toml, tauri.conf.json, package.json, snapcraft.yaml, both
Cargo.lock, package-lock.json), adds the 1.2.8 entry to the Flatpak
metainfo, and sets the About modal codename to "My QBZ".

cc

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "QBZ",
-  "version": "1.2.7",
+  "version": "1.2.8",
   "identifier": "com.blitzfc.qbz",
   "build": {
     "beforeDevCommand": "npm run dev",