♻️(backend) use Authorization header for LiveKit token authentication

Replace passing the LiveKit JWT in the request body with the
Authorization header, following standard authentication practices.

Extend the LiveKit authentication backend usage across additional
endpoints.

This also raises questions about how clients should securely
retrieve LiveKit tokens, to be addressed later.

src/frontend/src/features/rooms/api/renameParticipant.ts

@@ -17,9 +17,11 @@ export const useRenameParticipant = () => {
 
     return fetchApi(`rooms/${data.id}/rename/`, {
       method: 'POST',
+      headers: {
+        Authorization: `Bearer ${token}`,
+      },
       body: JSON.stringify({
         name,
-        token,
       }),
     })
   }

src/frontend/src/features/rooms/api/updateRaiseHand.ts

@@ -17,9 +17,11 @@ export const useRaiseHand = () => {
 
     return fetchApi(`rooms/${data.id}/toggle-hand/`, {
       method: 'POST',
+      headers: {
+        Authorization: `Bearer ${token}`,
+      },
       body: JSON.stringify({
         raised,
-        token,
       }),
     })
   }

src/frontend/src/features/subtitle/api/startSubtitle.ts

@@ -14,9 +14,9 @@ const startSubtitle = ({
 }: StartSubtitleParams): Promise<ApiRoom> => {
   return fetchApi(`rooms/${id}/start-subtitle/`, {
     method: 'POST',
-    body: JSON.stringify({
-      token,
-    }),
+    headers: {
+      Authorization: `Bearer ${token}`,
+    },
   })
 }