style: change room title and no meetings text to pure black

- Update room title in MinimalHeader from gray.700 to black
- Update 'No meetings right now' text from gray.700 to black
- Improves visual hierarchy and readability
- Consistent with other pages' styling

www/app/[roomName]/MeetingSelection.tsx

@@ -388,7 +388,7 @@ export default function MeetingSelection({
             <VStack gap={4}>
               <Icon as={FaCalendarAlt} boxSize="48px" color="gray.400" />
               <VStack gap={2}>
-                <Text fontSize="xl" fontWeight="semibold" color="gray.700">
+                <Text fontSize="xl" fontWeight="semibold" color="black">
                   No meetings right now
                 </Text>
                 <Text fontSize="md" color="gray.600" maxW="400px">

www/app/components/MinimalHeader.tsx

@@ -62,7 +62,7 @@ export default function MinimalHeader({
             alt="Reflector"
           />
         </Link>
-        <Text fontSize="lg" fontWeight="semibold" color="gray.700">
+        <Text fontSize="lg" fontWeight="semibold" color="black">
           {roomTitle}
         </Text>
       </Flex>