Merge Workstream H: device pairing UI + live dashboard

Resolved conflicts in App.tsx/SeancePage.tsx (both F and H added new
routes/nav links, kept both) and i18n files (both added sibling top-level
keys — inventory + devices, fixed nesting after conflict markers removed).

Also fixed a real integration gap: DevicesPage.test.tsx's mock User object
predated Workstream F's unlocks/essence additions to the User type (the
two workstreams built in parallel isolation and couldn't see each other's
changes). 269/269 frontend tests pass, tsc clean.

frontend/src/i18n/en.json

@@ -14,6 +14,7 @@
     "codex": "codex",
     "shop": "shop",
     "inventory": "inventory",
+    "devices": "devices",
     "seance": "séance",
     "enter": "enter",
     "logout": "depart"
@@ -443,6 +444,39 @@
       "error": "the sigil would not hold"
     }
   },
+  "devices": {
+    "back": "← the threshold",
+    "title": "DEVICE BAY",
+    "subtitle": "pair hardware to your account and watch its telemetry live",
+    "pair": {
+      "title": "PAIR A NEW DEVICE",
+      "nameLabel": "device name",
+      "namePlaceholder": "e.g. attic-node-01",
+      "submit": "pair device",
+      "pending": "pairing…",
+      "nameRequired": "name the device before pairing",
+      "error": "the pairing handshake failed — try again"
+    },
+    "token": {
+      "warning": "copy this now — it cannot be shown again. losing it means re-pairing the device.",
+      "copy": "copy",
+      "copied": "copied",
+      "confirm": "I've saved it — hide token"
+    },
+    "dashboard": {
+      "title": "LIVE FEED",
+      "empty": "no devices paired yet — pair one above to see it here",
+      "lastSeen": "last seen",
+      "lastSeenNever": "never",
+      "noReadings": "awaiting first reading…",
+      "connection": {
+        "connecting": "reaching the feed…",
+        "open": "feed live",
+        "unstable": "feed unstable…",
+        "closed": "feed offline"
+      }
+    }
+  },
   "haunting": {
     "whisper": {
       "behindYou": "behind you",