sway: screenshots, polkit floating, flatpak dark theme

Screenshots
- Swap xfce4-screenshooter for flameshot + grim/slurp/jq; xfce4 used
  the X11 selection so clipboard didn't round-trip to Wayland clients.
  Print invokes flameshot's editor; Shift/Alt+Print are quick
  grim-based captures via a small wrapper script. Flameshot is now
  autostarted so the first capture isn't slow.

Polkit
- Add for_window rules so the xfce-polkit dialog (and any other polkit
  agent) always opens floating.

Flatpak dark theme
- Write /etc/flatpak/overrides/global with GTK_THEME=Yaru-Blue-dark for
  legacy GTK apps, plus a sway-portals.conf so the Settings portal is
  served by xdg-desktop-portal-gtk (wlr doesn't implement it). That
  lets libadwaita apps see color-scheme=prefer-dark.

cleanup-sway: track the new package set.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ansible/roles/profile_desktop_common/tasks/main.yml

@@ -464,6 +464,28 @@
     - (desktop_flatpak_extensions | default([])) | length > 0
     - item | length > 0
 
+- name: Ensure /etc/flatpak/overrides exists
+  tags: [packages, flatpak, theme]
+  ansible.builtin.file:
+    path: /etc/flatpak/overrides
+    state: directory
+    owner: root
+    group: root
+    mode: "0755"
+  when: (desktop_flatpak_packages | default([])) | length > 0
+
+- name: Force dark GTK theme for Flatpak applications
+  tags: [packages, flatpak, theme]
+  ansible.builtin.copy:
+    dest: /etc/flatpak/overrides/global
+    content: |
+      [Environment]
+      GTK_THEME={{ desktop_flatpak_gtk_theme | default('Yaru-Blue-dark') }}
+    owner: root
+    group: root
+    mode: "0644"
+  when: (desktop_flatpak_packages | default([])) | length > 0
+
 - name: Bootstrap rustup toolchain installer
   tags: [packages]
   block: