Consolidate asset relationships onto the shared card

The curated Controlled Machines (PC detail) and Connected PC (machine
detail) cards duplicated what the generic relationships card already
shows with type badges and inline add/remove - and hid every
non-controls relationship type. Removed the curated cards and their
plumbing (~105 lines of orphaned CSS included); the MachineForm
controlling-PC picker stays as the write path. Also theme-variable
fixes on the shared card styling.

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

frontend/src/assets/style.css

@@ -1137,26 +1137,7 @@ td.actions {
   font-style: italic;
 }
 
-/* Connected Device */
-.connected-device {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  gap: 1rem;
-}
-
-.device-link {
-  display: flex;
-  align-items: center;
-  gap: 0.75rem;
-  text-decoration: none;
-  color: inherit;
-}
-
-.device-link:hover .device-name {
-  color: var(--info);
-}
-
+/* Device icon (network detail) */
 .device-icon {
   width: 44px;
   height: 44px;
@@ -1173,76 +1154,6 @@ td.actions {
   height: 24px;
 }
 
-.device-info {
-  display: flex;
-  flex-direction: column;
-}
-
-.device-name {
-  font-weight: 600;
-  font-size: 15px;
-}
-
-.device-alias {
-  font-size: 13px;
-  color: var(--text-light);
-}
-
-.connection-type {
-  padding: 0.25rem 0.5rem;
-  font-size: 11px;
-  background: rgba(4, 185, 98, 0.2);
-  color: var(--success);
-  border-radius: 0.25rem;
-}
-
-/* Equipment List */
-.equipment-list {
-  display: flex;
-  flex-direction: column;
-  gap: 0.5rem;
-}
-
-.equipment-item {
-  display: flex;
-  align-items: center;
-  justify-content: space-between;
-  padding: 0.75rem;
-  background: var(--bg);
-  border: 1px solid var(--border);
-  border-radius: 0.25rem;
-  text-decoration: none;
-  color: inherit;
-  transition: border-color 0.15s;
-}
-
-.equipment-item:hover {
-  border-color: var(--primary);
-}
-
-.equipment-info {
-  display: flex;
-  flex-direction: column;
-}
-
-.equipment-name {
-  font-weight: 500;
-  font-size: 14px;
-}
-
-.equipment-alias {
-  font-size: 13px;
-  color: var(--text-light);
-}
-
-.connection-tag {
-  padding: 0.2rem 0.5rem;
-  font-size: 11px;
-  background: rgba(4, 185, 98, 0.2);
-  color: var(--success);
-  border-radius: 0.25rem;
-}
-
 /* Network */
 .network-list {
   display: flex;