remove obsolete skipped tests; fix billboard applet menu containment; align landscape menus

Deleted skips:
- test_fan_next_button_advances_card (T11) + test_fan_remembers_position_on_reopen (T13):
  fan-nav nav button obstruction — deferred indefinitely, not worth tracking
- test_selected_sig_card_removed_from_deck_for_other_gamers (S5): card count
  mismatch in channels context — grand overhaul pending, obsolete with new sig-select
- Removed stale TODO comment about #id_inv_sig_card (element no longer exists)
- Dropped unused `import unittest` from test_room_sig_select.py

billboard applet menu fix: moved #id_billboard_applet_menu out of
#id_billboard_applets_container — container-type:inline-size was making the
container a containing block for fixed-position descendants, clipping the menu.

Landscape menu alignment: all applet menus now right:0.5rem (flush with gear/kit
buttons in the 4rem right sidebar); added #id_room_menu to the landscape rule.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/static_src/scss/_applets.scss

@@ -129,9 +129,10 @@
     #id_game_applet_menu,
     #id_game_kit_menu,
     #id_wallet_applet_menu,
+    #id_room_menu,
     #id_billboard_applet_menu {
-        right: calc(#{$sidebar-w} + 1rem);
-        bottom: 6.6rem;         // same as portrait, just shifted right of footer sidebar
+        right: 0.5rem;
+        bottom: 6.6rem;
         top: auto;
     }
 }