refactor: convert color system to RGB channels for native Tailwind opacity

Root cause fix for all broken CSS variable opacity modifiers. Converted
every hex CSS variable to space-separated RGB channels (e.g. #fda4af →
253 164 175) and updated Tailwind config to use rgb(var(...) / <alpha-value>).
This makes bg-accent-rose/10, border-border-hard/50, etc. work natively
everywhere — no more currentColor fallback. Reverted all previous explicit
rgba() workarounds back to clean Tailwind syntax. Also fixed the voice
connection wifi icon SVG (was bottom-left aligned, now centered).

packages/web/src/components/layout/MemberSidebar.tsx

@@ -15,7 +15,7 @@ function getMemberGroup(member: MemberWithUser, ownerId: string | undefined) {
     return {
       key: '__owner__',
       label: 'OWNER',
-      color: ownerRole?.color ?? 'var(--accent-rose)',
+      color: ownerRole?.color ?? 'rgb(var(--accent-rose))',
       position: Infinity,
     };
   }
@@ -79,7 +79,7 @@ export function MemberSidebar() {
       return { color: sorted[0]!.color };
     }
     if (ownerId && member.userId === ownerId) {
-      return { color: 'var(--accent-rose)' };
+      return { color: 'rgb(var(--accent-rose))' };
     }
     return undefined;
   };