feat: fullscreen stream on admin home, fix card titles 2-line clamp

- Remove greeting for admin view, render stream fullscreen (no scroll)
- AdminHome: stream fills full viewport height via flex layout
- StreamEmbed: fills parent height instead of fixed aspect-ratio
- Set Twitch channel to lofigirl
- CourseCard: clamp title to 2 lines with fixed min-height

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/CourseCard.vue

@@ -66,11 +66,11 @@
 
 		<!-- Card body -->
 		<div class="flex flex-col flex-1 p-4">
-			<!-- Title (when image present) -->
+			<!-- Title (when image present): max 2 lines -->
 			<div
 				v-if="course.image"
-				class="font-semibold text-ink-gray-9 leading-snug mb-1"
-				:class="course.title.length > 40 ? 'text-sm' : 'text-base'"
+				class="font-semibold text-ink-gray-9 leading-snug mb-1 line-clamp-2 text-sm"
+				style="min-height: 2.5rem"
 			>
 				{{ course.title }}
 			</div>