Migrate to bread-utils: Hyprland IPC, single-instance lock, popup scaffold, XDG paths

Mirrors tonight's breadbox migration (same shared crate, same duplicated
patterns):

- position.rs's raw socket1 client -> bread_utils::hypr (file removed
  entirely, its logic now lives in the shared crate)
- toggle_or_continue's TOCTOU-prone PID-file dance -> bread_utils::singleton
- the layer-shell window setup, Up/Down visible-row navigation, and
  click-outside-close gesture -> bread_utils::gtk_popup
- breadclip-core's data_dir(): replaced the buggy
  `dirs::data_local_dir().unwrap_or_else(|| PathBuf::from("~/.local/share"))`
  fallback (flagged but never fixed in tonight's earlier audit pass —
  PathBuf never expands `~`) with bread_utils::xdg::data_dir, which
  resolves a real $HOME before ever falling back.

Builds and tests clean across the whole breadclip workspace.

Cargo.lock

@@ -46,11 +46,23 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "bread-utils"
+version = "0.2.3"
+dependencies = [
+ "dirs",
+ "gtk4",
+ "gtk4-layer-shell",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "breadclip"
 version = "0.1.1"
 dependencies = [
  "bread-theme",
+ "bread-utils",
  "breadclip-core",
  "gtk4",
  "gtk4-layer-shell",
@@ -61,6 +73,7 @@ dependencies = [
 name = "breadclip-core"
 version = "0.1.0"
 dependencies = [
+ "bread-utils",
  "dirs",
  "hex",
  "rusqlite",