perf(P6B.T10): i18next tree-shake — prune dead locale keys

Audited all four i18next namespaces (common, auth, errors, app) against
static t() call-site grep across the entire desktop source tree.
Pruned 40 dead keys per locale, 80 total lines removed across 6 files.

Dead keys removed:
- app: call.{e2ee_active_hint,still_live,voice_connected},
       chats.{show_archived,show_active}, admin.nav,
       friends.confirm_unfriend, settings.{danger_zone,this_device,
       presence,section_ringtone}
- auth: signed_in.{title,session_active,user_id,admin,yes,no,sign_out,
        device_active,device_platform,device_registered_at},
        entire device.* section (old device-registration UI)
- common: loading, cancel, retry, online, offline, idle, dnd, invisible

Dynamic-key patterns were found and respected: t('errors:'+code)
keeps all errors keys; t('app:presence.'+val) keeps all presence keys;
t('app:annotator.tool.'+id) uses defaultValue so its locale entries
were not required.

packages/shared/src/i18n/locales/en/app.json

@@ -53,8 +53,6 @@
     "archive": "Archive",
     "unarchive": "Unarchive",
     "archived_title": "Archive",
-    "show_archived": "Show archive",
-    "show_active": "Show active",
     "archived_empty_title": "Nothing archived",
     "archived_empty_subtitle": "Archived conversations appear here.",
     "mute": "Mute",
@@ -84,8 +82,6 @@
     "join": "Join",
     "in_call": "In call",
     "waiting_for_peers": "Waiting for others…",
-    "voice_connected": "Voice connected",
-    "still_live": "Call still live",
     "share_screen": "Share screen",
     "stop_share_screen": "Stop sharing",
     "is_sharing_screen": "{{name}} is sharing their screen",
@@ -133,11 +129,9 @@
     "action_unfriend": "Unfriend",
     "action_accept": "Accept",
     "action_decline": "Decline",
-    "action_cancel": "Cancel",
-    "confirm_unfriend": "Remove this friend?"
+    "action_cancel": "Cancel"
   },
   "admin": {
-    "nav": "Admin",
     "title": "Admin panel",
     "settings_title": "Global settings",
     "invites_enabled": "Allow new signups",
@@ -188,15 +182,11 @@
     "screen_share_quality": "Quality",
     "screen_share_hint": "WebRTC dynamically adjusts bitrate + resolution to match network conditions (SVC/VP9). Values are upper bounds. Changes apply on the next call.",
     "language": "Language",
-    "presence": "Presence",
     "show_read_receipts": "Show read receipts",
     "show_read_receipts_hint": "When off, others can't see when you read their messages — and you won't see when they read yours.",
     "allow_dms_strangers": "Allow DMs from strangers",
     "allow_dms_strangers_hint": "When off, only friends can DM you.",
-    "this_device": "This device",
-    "danger_zone": "Danger zone",
     "sign_out": "Sign out",
-    "section_ringtone": "Ringtone",
     "ringtone_incoming": "Incoming call",
     "ringtone_default_active": "Default ringtone (double beep)",
     "ringtone_custom_active": "{{name}} · {{size}} MB",

packages/shared/src/i18n/locales/en/auth.json

@@ -50,28 +50,8 @@
   "footer_studio": "Supabase Studio",
   "legal_note": "By signing up you accept that the server sees only ciphertext.",
   "signed_in": {
-    "title": "Signed in",
-    "session_active": "Session active",
-    "user_id": "User ID",
     "email": "Email",
     "username": "Username",
-    "display_name": "Display name",
-    "admin": "Admin",
-    "yes": "yes",
-    "no": "no",
-    "sign_out": "Sign out",
-    "device_active": "Active device",
-    "device_platform": "Platform",
-    "device_registered_at": "Registered"
-  },
-  "device": {
-    "title": "Register this device",
-    "subtitle": "Generates an X25519 keypair. Private key stays on this device.",
-    "name_label": "Device name",
-    "name_hint": "Shown to you in your device list. Keep it recognisable.",
-    "name_placeholder": "Dennis Laptop",
-    "cta": "Register device",
-    "cta_loading": "Generating keypair…",
-    "security_note_dev": "Dev build: private key stored unencrypted in localStorage. Stronghold comes before release."
+    "display_name": "Display name"
   }
 }

packages/shared/src/i18n/locales/en/common.json

@@ -1,16 +1,8 @@
 {
   "app_name": "ChatApp",
-  "loading": "Loading…",
   "finalising_session": "Finalising session…",
-  "cancel": "Cancel",
   "save": "Save",
   "close": "Close",
-  "retry": "Retry",
-  "online": "Online",
-  "offline": "Offline",
-  "idle": "Idle",
-  "dnd": "Do not disturb",
-  "invisible": "Invisible",
   "local_stack_online": "local stack online",
   "dev_build": "dev build"
 }