Tie flashpasted to graphical-session.target

The unit needs Wayland and X11 to be available before it starts —
without a graphical session, both `wl-clipboard-rs` and the X11
selection owner have nothing to bind to. `default.target` activates at
login, which is too early on this stack (Wayland comes up shortly
after, and the early daemon then sits without a usable display). Move
to `graphical-session.target` so systemd starts the daemon once the
display is actually live; keeps the docs in sync with the shipped unit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: NagyVikt

docs/install.md

@@ -130,7 +130,7 @@ RestartSec=2
 Environment=RUST_LOG=info
 
 [Install]
-WantedBy=default.target
+WantedBy=graphical-session.target
 EOF
 systemctl --user daemon-reload
 systemctl --user enable --now flashpasted.service

systemd/flashpasted.service

@@ -12,4 +12,4 @@ RestartSec=2
 Environment=RUST_LOG=info
 
 [Install]
-WantedBy=default.target
+WantedBy=graphical-session.target