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/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>