fix: add missing DELETE handler and fix comment delete/vote URLs (web + iOS)

The /api/comments/[id] delete route was never created; the deleteComment helper
in pocketbase.ts existed but was unreachable. Added DELETE /api/comment/[id]
route handler alongside the existing vote route. Updated CommentsSection.svelte
and iOS APIClient to use /api/comment/{id} for both delete and (already fixed)
vote, keeping all comment-mutation endpoints under the singular /api/comment/
prefix to avoid SvelteKit route conflicts with /api/comments/[slug].

ui/src/lib/components/CommentsSection.svelte

@@ -156,7 +156,7 @@
 		if (deletingIds.has(commentId)) return;
 		deletingIds = new Set([...deletingIds, commentId]);
 		try {
-			const res = await fetch(`/api/comments/${commentId}`, { method: 'DELETE' });
+			const res = await fetch(`/api/comment/${commentId}`, { method: 'DELETE' });
 			if (!res.ok) return;
 			if (parentId) {
 				// Remove reply from parent

ui/src/routes/api/comment/[id]/+server.ts

@@ -0,0 +1,26 @@
+import { error } from '@sveltejs/kit';
+import type { RequestHandler } from './$types';
+import { deleteComment } from '$lib/server/pocketbase';
+import { log } from '$lib/server/logger';
+
+/**
+ * DELETE /api/comment/[id]
+ * Deletes a comment and its replies. Only the comment owner may delete.
+ * Requires authentication.
+ */
+export const DELETE: RequestHandler = async ({ params, locals }) => {
+	if (!locals.user) error(401, 'Login required');
+
+	const { id } = params;
+
+	try {
+		await deleteComment(id, locals.user.id);
+		return new Response(null, { status: 204 });
+	} catch (e) {
+		const msg = String(e);
+		if (msg.includes('Not authorized')) error(403, 'Not authorized to delete this comment');
+		if (msg.includes('not found')) error(404, 'Comment not found');
+		log.error('api/comment/[id]', 'deleteComment failed', { id, err: msg });
+		error(500, 'Failed to delete comment');
+	}
+};