refactor(labels): purge legacy /label/get stack

/label/get is gone from the Qobuz v9.7.0.3 Android app (source:
c30/b.java doesn't declare it anymore). With the Qobuz beta rollout
the server-side deprecation timer is probably running, so we yank our
dependency now.

Removed:
- LABEL_GET path constant (qbz-qobuz + src-tauri/api)
- get_label() client method (qbz-qobuz + src-tauri/api)
- get_label() wrapper in QbzCore + CoreBridge
- v2_get_label tauri command + its lib.rs registration
- LabelDetail backend type (qbz-models + src-tauri/api/models)
- commands::search::get_label (dead, was never registered)
- Unused LabelDetail import in src/routes/+page.svelte

Preserved:
- Frontend LabelDetail interface (it's a UI view-model shaped by
  LabelReleasesView, not a backend contract)
- /api/labels/{id} HTTP route on qbzd — now composes /label/page +
  /label/getAlbums internally so external HTTP clients still see the
  same { id, name, description, image, albums: { items, total, ... } }
  shape

cc

crates/qbz-models/src/lib.rs

@@ -66,7 +66,6 @@ pub use types::{
     GenreListResponse,
     ImageSet,
     Label,
-    LabelDetail,
     LabelExploreResponse,
     LabelGetListResponse,
     LabelListPage,

crates/qbz-models/src/types.rs

@@ -422,17 +422,6 @@ pub struct Label {
     pub name: String,
 }
 
-/// Label detail with albums
-#[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct LabelDetail {
-    pub id: u64,
-    pub name: String,
-    pub description: Option<String>,
-    pub image: Option<ImageSet>,
-    pub albums: Option<SearchResultsPage<Album>>,
-    pub albums_count: Option<u32>,
-}
-
 // ============ Label Page Types (/label/page) ============
 
 /// Top-level response from /label/page