feat(groups): audio and video calls in group chats; release v6.6.6

A group call is N-1 ordinary 1:1 calls, one to each other member, each riding
the pairwise session that member already has — a transport a human already
authenticated by comparing the safety code. No mixer, no SFU, no point at which
two people's media meets anywhere but on a device.

Call control is separate from call media, because the two reach different sets
of people. Who opened a call, who joined and who left travels as group frames
signed with the sender's group identity key, so it reaches members currently
reachable only through a relay — and a relaying member can drop one but cannot
write one. Media flows only where a direct link exists, so a member without one
shows as connecting rather than being omitted. Frames carry a per-sender
sequence checked before the action, so a captured leave cannot end a later call,
and simultaneous calls converge on the lower random call id.

One capture is shared across every leg rather than one getUserMedia per member,
and legs answer without prompting: the flag permitting that is set only locally,
only while this user is in the call, and cleared when they leave.

UI: a gallery that sizes itself from the space it has, a spotlight view, an
active-speaker indicator read from the waveform, and the call surface in the
same visual language as the 1:1 one.

Also in this commit, the v6.5.0 language-suggestion work that had not been
pushed yet; its notes are in the changelog. And two fixes: the safety-code input
asks for digits rather than text, and starting a new chat from inside a group no
longer creates it behind the group where it cannot be seen — which had made it
impossible to connect to anyone new, or to add anyone to a group, while a group
was open.

Claude-Session: https://claude.ai/code/session_01XSxAkET3hQTkYDQfbjCQwZ

locales/ar.json

@@ -36,6 +36,9 @@
   },
   "ui": {
     "language.label": "اللغة",
+    "language.suggest.text": "هذه الصفحة متوفرة أيضًا بالعربية.",
+    "language.suggest.cta": "اقرأ بالعربية",
+    "language.suggest.dismiss": "إغلاق",
     "community.title": "انضمّ إلى مستقبل الخصوصية",
     "community.description": "ينمو SecureBit بفضل مجتمعه. أفكاركم وملاحظاتكم هي ما يصوغ مستقبل التواصل الآمن - مبنيّ في العلن، مع تحقّق ASN.1 كامل من طرف إلى طرف.",
     "community.github": "مستودع GitHub",
@@ -781,6 +784,28 @@
     "offline.disconnect": "قطع الاتصال",
     "offline.learnMore": "اعرف المزيد",
     "pwa.installApp": "ثبّت التطبيق",
-    "chat.onWeb": "أنت على الويب"
+    "chat.onWeb": "أنت على الويب",
+    "groupCall.startVoice": "بدء مكالمة صوتية جماعية",
+    "groupCall.startVideo": "بدء مكالمة فيديو جماعية",
+    "groupCall.join": "انضمام",
+    "groupCall.dismiss": "ليس الآن",
+    "groupCall.leave": "مغادرة المكالمة",
+    "groupCall.you": "أنت",
+    "groupCall.connecting": "جارٍ الاتصال…",
+    "groupCall.waitingLink": "في انتظار رابط مباشر…",
+    "groupCall.legFailed": "تعذّر الاتصال",
+    "groupCall.startedVoice": "بدأ {name} مكالمة صوتية",
+    "groupCall.startedVideo": "بدأ {name} مكالمة فيديو",
+    "groupCall.inCall": "{count} في المكالمة",
+    "groupCall.err.permission_denied": "تعذّر بدء المكالمة - الوصول إلى الميكروفون والكاميرا محظور. اسمح به لهذا الموقع ثم أعد المحاولة.",
+    "groupCall.err.device_not_found": "تعذّر بدء المكالمة - لم يُعثر على ميكروفون في هذا الجهاز.",
+    "groupCall.err.device_busy": "تعذّر بدء المكالمة - الميكروفون مستخدَم من تطبيق آخر. أغلقه ثم أعد المحاولة.",
+    "groupCall.err.media_failed": "تعذّر بدء المكالمة - لم يمكن فتح الميكروفون.",
+    "groupCall.err.call_in_progress": "هناك مكالمة جارية بالفعل في هذه المجموعة. انضم إليها بدل بدء أخرى.",
+    "groupCall.err.not_ready": "أكّد رمز المجموعة قبل الاتصال.",
+    "groupCall.speaking": "{name} يتحدّث الآن",
+    "groupCall.pin": "عرض {name} بحجم كبير",
+    "groupCall.unpin": "العودة إلى الجميع",
+    "groupCall.showEveryone": "الجميع"
   }
 }