feat(voice): Redesign call widget and in-thread call bubbles

Brings the floating call widget and in-thread voice-call bubbles in
line with the new Figma design across Twilio and WhatsApp, light and
dark.

- New CallCard component for the floating widget with incoming /
  outgoing / ongoing states, rounded-square avatar, status badges,
  duration timer, and "Go to conversation thread" footer.
- Floating widget header now shows the contact's city, country, and
  country flag (derived from country_code) when available, falling
  back to the channel icon + inbox name.
- In-thread VoiceCall bubble redesigned: 44x44 tonal icon container,
  title + duration/subtext, audio player + transcript when a
  recording exists, and a "Call back" pill for missed inbound calls.
- isOutbound on the call bubble now accepts both outgoing/outbound
  and incoming/inbound spellings and falls back to message
  orientation, so the label can no longer disagree with which side
  of the thread the bubble sits on.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/javascript/dashboard/i18n/locale/en/conversation.json

@@ -89,7 +89,8 @@
       "THEY_ANSWERED": "They answered",
       "YOU_ANSWERED": "You answered",
       "AGENT_ANSWERED": "{agentName} answered",
-      "JOIN_CALL": "Join call"
+      "JOIN_CALL": "Join call",
+      "CALL_BACK": "Call back"
     },
     "HEADER": {
       "RESOLVE_ACTION": "Resolve",
@@ -311,7 +312,8 @@
       "END_CALL": "End call",
       "MUTE": "Mute mic",
       "UNMUTE": "Unmute mic",
-      "VIEW_CHAT_HISTORY": "View chat history"
+      "VIEW_CHAT_HISTORY": "View chat history",
+      "GO_TO_CONVERSATION": "Go to conversation thread"
     }
   },
   "EMAIL_TRANSCRIPT": {