chore(release): bump version to 1.2.10 + tag notes

Hotfix on top of 1.2.9 to address the gapless-play regression
introduced by dee987c1a's tightened isGaplessTransition gate combined
with a long-standing race in the player's transition-swap atomics.

Bumped:
- src-tauri/Cargo.toml + Cargo.lock
- src-tauri/tauri.conf.json
- package.json + package-lock.json
- snapcraft.yaml (version + source-tag) — packaging/snap/snapcraft.yaml
  follows automatically via symlink
- packaging/flatpak/com.blitzfc.qbz.metainfo.xml (new release entry)

cc

src-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "qbz-nix"
-version = "1.2.9"
+version = "1.2.10"
 description = "Native high-fidelity client for Qobuz™ subscribers on Linux with Hi-Fi audio support (uses the Qobuz API; not certified by Qobuz)"
 authors = ["blitzkriegfc"]
 edition = "2021"