feat(home): add pyclipsync clipboard sync service for niri

xwayland-satellite has no compositor-level clipboard bridging, so X11
clients (WeChat/QQ) and Wayland clients cannot see each other's clipboard.
Add the pyclipsync flake input and enable its home-manager module, which
installs the daemon as a systemd user service bound to the graphical session.

flake.nix

@@ -168,5 +168,11 @@
       url = "github:ryan4yin/nur-packages";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    # Wayland <-> X11 clipboard sync daemon for xwayland-satellite (niri)
+    pyclipsync = {
+      url = "github:ryan4yin/pyclipsync";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 }