Migrate socket2 path resolution to bread-utils::hypr

hyprland_socket2_path() duplicated the same HYPRLAND_INSTANCE_SIGNATURE +
XDG_RUNTIME_DIR resolution breadbox and breadclip had for socket1 — now
shared via bread_utils::hypr::socket_path (path dependency for now, see
the TODO in Cargo.toml).

Builds and all 16 existing tests pass.

Cargo.lock

@@ -20,11 +20,21 @@ version = "2.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b4388bee8683e3d04af747c73422af53102d2bd24d9eadb6cbc100baef4b43f8"
 
+[[package]]
+name = "bread-utils"
+version = "0.2.3"
+dependencies = [
+ "dirs",
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "breadmon"
 version = "0.1.1"
 dependencies = [
  "anyhow",
+ "bread-utils",
  "crossterm",
  "dirs",
  "futures",