feat: implement gallery feed with social features and SSE

- Cursor-based feed endpoint using v_feed view with hashtag filtering
- Like toggle (INSERT ON CONFLICT), comments CRUD
- Feed delta endpoint for SSE-driven incremental updates
- SSE client with Page Visibility API (pause/reconnect)
- Responsive photo/video grid with infinite scroll
- Hashtag filter chips, lightbox modal with comments
- Media file serving via tower-http ServeDir

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

frontend/src/lib/components/FeedGrid.svelte

@@ -0,0 +1,80 @@
+<script lang="ts">
+	import type { FeedUpload } from '$lib/types';
+
+	interface Props {
+		uploads: FeedUpload[];
+		onlike: (id: string) => void;
+		oncomment: (id: string) => void;
+		onselect: (upload: FeedUpload) => void;
+	}
+
+	let { uploads, onlike, oncomment, onselect }: Props = $props();
+
+	function isVideo(mime: string): boolean {
+		return mime.startsWith('video/');
+	}
+
+	function imageUrl(upload: FeedUpload): string {
+		if (upload.thumbnail_url) return upload.thumbnail_url;
+		if (upload.preview_url) return upload.preview_url;
+		return '';
+	}
+</script>
+
+<div class="grid grid-cols-2 gap-2 sm:grid-cols-3">
+	{#each uploads as upload (upload.id)}
+		<div class="group relative aspect-square cursor-pointer overflow-hidden rounded-lg bg-gray-100">
+			<button
+				onclick={() => onselect(upload)}
+				class="block h-full w-full"
+				aria-label="Upload anzeigen"
+			>
+				{#if isVideo(upload.mime_type)}
+					<div class="flex h-full items-center justify-center bg-gray-800">
+						{#if imageUrl(upload)}
+							<img src={imageUrl(upload)} alt="" class="h-full w-full object-cover" />
+						{/if}
+						<div class="absolute inset-0 flex items-center justify-center">
+							<svg class="h-10 w-10 text-white/80" fill="currentColor" viewBox="0 0 24 24">
+								<path d="M8 5v14l11-7z" />
+							</svg>
+						</div>
+					</div>
+				{:else if imageUrl(upload)}
+					<img src={imageUrl(upload)} alt="" class="h-full w-full object-cover" loading="lazy" />
+				{:else}
+					<div class="flex h-full items-center justify-center text-gray-400">
+						<svg class="h-8 w-8" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+							<path stroke-linecap="round" stroke-linejoin="round" stroke-width="1.5" d="M4 16l4.586-4.586a2 2 0 012.828 0L16 16m-2-2l1.586-1.586a2 2 0 012.828 0L20 14m-6-6h.01M6 20h12a2 2 0 002-2V6a2 2 0 00-2-2H6a2 2 0 00-2 2v12a2 2 0 002 2z" />
+						</svg>
+					</div>
+				{/if}
+			</button>
+
+			<!-- Overlay with name and stats -->
+			<div class="pointer-events-none absolute inset-x-0 bottom-0 bg-gradient-to-t from-black/60 to-transparent p-2">
+				<p class="truncate text-xs font-medium text-white">{upload.uploader_name}</p>
+				<div class="mt-0.5 flex items-center gap-3 text-xs text-white/80">
+					<button
+						class="pointer-events-auto flex items-center gap-0.5"
+						onclick={(e) => { e.stopPropagation(); onlike(upload.id); }}
+					>
+						<svg class="h-3.5 w-3.5 {upload.liked_by_me ? 'fill-red-400 text-red-400' : ''}" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+							<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4.318 6.318a4.5 4.5 0 000 6.364L12 20.364l7.682-7.682a4.5 4.5 0 00-6.364-6.364L12 7.636l-1.318-1.318a4.5 4.5 0 00-6.364 0z" />
+						</svg>
+						{upload.like_count}
+					</button>
+					<button
+						class="pointer-events-auto flex items-center gap-0.5"
+						onclick={(e) => { e.stopPropagation(); oncomment(upload.id); }}
+					>
+						<svg class="h-3.5 w-3.5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+							<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 12h.01M12 12h.01M16 12h.01M21 12c0 4.418-4.03 8-9 8a9.863 9.863 0 01-4.255-.949L3 20l1.395-3.72C3.512 15.042 3 13.574 3 12c0-4.418 4.03-8 9-8s9 3.582 9 8z" />
+						</svg>
+						{upload.comment_count}
+					</button>
+				</div>
+			</div>
+		</div>
+	{/each}
+</div>