Fix PC installed-applications rendering; minor UI cleanups

The PC detail Installed Applications section 500d and vanished on any
real PC: ComputerInstalledApp had no to_dict, so the endpoint errored
and the v-if hid the section. Added the serializer (curated version
wins over the raw collected string, app name + description included)
and aligned PCDetail to the flat payload; regression test added.

Also: employee detail skips its USB panels when the usb plugin is
disabled (was firing 404s), and the shopfloor kiosk header is now
light-on-dark for readability.

810 tests pass; PC 259 installed apps verified live.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -10,6 +10,16 @@ ADR-007 and ADR-002.
 
 ## [Unreleased]
 
+### Fixed
+
+- PC detail Installed Applications no longer 500s and silently disappears on
+  real PCs (ComputerInstalledApp had no to_dict); the section renders app
+  name, version, and description again.
+- Employee detail skips its USB panels when the usb plugin is disabled (no
+  more 404 console noise).
+- Shopfloor kiosk header text is readable (light on the dark navy header).
+
+
 ### Added
 
 - Single-label sheet-position printing. The single asset-label page