feat(web): display arrangement table — the Stage 5 console x/y editor

Completes Stage 5's web piece (design/display-management.md §6.2): a `DisplayArrangement`
editor in the Virtual displays card. For a ≥2-display group, it renders an x/y table over
the live displays that carry a stable identity slot (the manual-layout key), seeded from
the current computed positions; Save writes `PUT /display/layout` (via the generated
`useSetDisplayLayout`), which switches the host to a manual layout applied from the next
connect. Shared/anonymous displays (no identity slot) are omitted (they can't be pinned).

Also refreshes the now-stale `display_pending_note` copy (conflict/identity/layout ARE
enforced as of Stages 3-5) in en + de.

web tsc + vite build green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/messages/de.json

@@ -67,7 +67,7 @@
 	"display_max": "Max. Displays",
 	"display_save": "Speichern",
 	"display_effective": "Aktiv",
-	"display_pending_note": "Konfliktbehandlung, Identität und Layout werden gespeichert, aber noch nicht angewendet — sie folgen in späteren Versionen.",
+	"display_pending_note": "Änderungen greifen ab der nächsten Verbindung — eine laufende Sitzung behält die Anzeige, mit der sie gestartet ist.",
 	"display_live": "Aktive Displays",
 	"display_none_live": "Derzeit keine virtuellen Displays.",
 	"display_state_active": "Aktiv",
@@ -77,6 +77,9 @@
 	"display_release_all": "Alle gehaltenen freigeben",
 	"display_expires_in": "Abbau in {sec}s",
 	"display_sessions": "{count} streamend",
+	"display_arrange": "Anzeigen anordnen",
+	"display_arrange_help": "Legen Sie fest, wo jede gestreamte Anzeige auf dem Desktop sitzt (in Pixeln). Beim Speichern wird auf ein manuelles Layout umgeschaltet; es greift ab der nächsten Verbindung.",
+	"display_arrange_save": "Anordnung speichern",
 	"clients_title": "Gekoppelte Geräte",
 	"clients_empty": "Noch keine gekoppelten Geräte.",
 	"clients_name": "Name",

web/messages/en.json

@@ -67,7 +67,7 @@
 	"display_max": "Max displays",
 	"display_save": "Save",
 	"display_effective": "In effect",
-	"display_pending_note": "Conflict handling, identity, and layout are stored but not enforced yet — they arrive in later releases.",
+	"display_pending_note": "Changes apply from the next connection — a streaming session keeps the display it opened on.",
 	"display_live": "Live displays",
 	"display_none_live": "No virtual displays right now.",
 	"display_state_active": "Active",
@@ -77,6 +77,9 @@
 	"display_release_all": "Release all kept",
 	"display_expires_in": "tears down in {sec}s",
 	"display_sessions": "{count} streaming",
+	"display_arrange": "Arrange displays",
+	"display_arrange_help": "Set where each streamed display sits on the desktop, in pixels. Saving switches to a manual layout; it applies from the next connect.",
+	"display_arrange_save": "Save arrangement",
 	"clients_title": "Paired clients",
 	"clients_empty": "No paired clients yet.",
 	"clients_name": "Name",