feat: close #54 V2 install safety, #33 rofi scrollbar, #43 MOTD tip

#54: permanent checks.installer-safety; test-install-safety harness with
offline compose-fail, LUKS-signature disk warn, and HM-hint FORCE paths.
#33: enable themed rofi scrollbars (generated + all whole-swap .rasi).
#43: MOTD + first-boot tip for System › Firmware (V3 LVFS stays hw-queue).

V2: compose-fail/disk-warn/hm-hint logs green offline; theme-shot
boreal+summer-night menus OK. V0 flake/installer-safety.

themes/neon-glass/rofi.rasi

@@ -49,7 +49,7 @@ entry {
 listview {
     lines: 7;
     spacing: 8px;
-    scrollbar: false;
+    scrollbar: true;
     border: 0px;
 }
 
@@ -83,3 +83,11 @@ element-text {
 element-text selected {
     text-color: var(accent, #00F0FF);
 }
+
+scrollbar {
+    width: 4px;
+    handle-width: 4px;
+    handle-color: rgba(0, 240, 255, 0.8);
+    background-color: rgba(21, 26, 34, 0.5);
+    border: 0px;
+}