feat: add Cloudflare AI TTS engine (aura-2-en) with voice grouping in UI

ui/src/lib/components/AudioPlayer.svelte

@@ -86,6 +86,7 @@
 	// ── Derived: voices grouped by engine ──────────────────────────────────
 	const kokoroVoices = $derived(voices.filter((v) => v.engine === 'kokoro'));
 	const pocketVoices = $derived(voices.filter((v) => v.engine === 'pocket-tts'));
+	const cfaiVoices = $derived(voices.filter((v) => v.engine === 'cfai'));
 
 	// ── Voice selector state ────────────────────────────────────────────────
 	let showVoicePanel = $state(false);
@@ -98,6 +99,7 @@
 	 * Human-readable label for a voice.
 	 * Kokoro: "af_bella" → "Bella (US F)"
 	 * Pocket-TTS: "alba" → "Alba (EN F)"
+	 * CF AI: "cfai:luna" → "Luna (EN F)"
 	 * Falls back gracefully if called with a bare string (e.g. from the store default).
 	 */
 	function voiceLabel(v: Voice | string): string {
@@ -110,6 +112,14 @@
 			return kokoroLabelFromId(v);
 		}
 
+		if (v.engine === 'cfai') {
+			// "cfai:luna" → "Luna (EN F)"
+			const speaker = v.id.startsWith('cfai:') ? v.id.slice(5) : v.id;
+			const name = speaker.replace(/\b\w/g, (c) => c.toUpperCase());
+			const genderLabel = v.gender.toUpperCase();
+			return `${name} (EN ${genderLabel})`;
+		}
+
 		if (v.engine === 'pocket-tts') {
 			const langLabel = v.lang.toUpperCase().replace('-', '');
 			const genderLabel = v.gender.toUpperCase();
@@ -844,6 +854,16 @@
 						{@render voiceRow(v)}
 					{/each}
 				{/if}
+
+				<!-- Cloudflare AI section -->
+				{#if cfaiVoices.length > 0}
+					<div class="px-3 py-1.5 bg-(--color-surface-2)/70 border-b border-(--color-border)/50 {kokoroVoices.length > 0 || pocketVoices.length > 0 ? 'border-t border-(--color-border)' : ''}">
+						<span class="text-[10px] font-semibold text-(--color-muted) uppercase tracking-widest">Cloudflare AI</span>
+					</div>
+					{#each cfaiVoices as v (v.id)}
+						{@render voiceRow(v)}
+					{/each}
+				{/if}
 			</div>
 			<div class="px-3 py-2 border-t border-(--color-border) bg-(--color-surface-2)/50">
 				<p class="text-xs text-(--color-muted)">