feat(settings): YouTube indirme ayarları ekle

Kullanıcıların YouTube indirme tercihlerini yapılandırabilmesi için ayarlar
arayüzüne yeni kontroller eklendi:

- Video çözünürlüğü seçimi (1080p, 720p, 480p, 360p, 240p, 144p)
- Sadece ses indirme seçeneği
- Ayarları kaydetme/yenileme butonları
- API ile entegrasyon için load/save fonksiyonları

client/src/routes/Settings.svelte

@@ -13,6 +13,11 @@
   let cookiesUpdatedAt = null;
   let loadingCookies = false;
   let savingCookies = false;
+  let loadingYtSettings = false;
+  let savingYtSettings = false;
+  let selectedResolution = "1080p";
+  let onlyAudio = false;
+  const resolutionOptions = ["1080p", "720p", "480p", "360p", "240p", "144p"];
   let error = null;
   let success = null;
 
@@ -64,8 +69,51 @@
     }
   }
 
+  async function loadYoutubeSettings() {
+    loadingYtSettings = true;
+    error = null;
+    try {
+      const resp = await apiFetch("/api/youtube/settings");
+      if (!resp.ok) throw new Error(`HTTP ${resp.status}`);
+      const data = await resp.json();
+      if (data?.resolution) selectedResolution = data.resolution;
+      if (typeof data?.onlyAudio === "boolean") onlyAudio = data.onlyAudio;
+    } catch (err) {
+      error = err?.message || "YouTube ayarları alınamadı.";
+    } finally {
+      loadingYtSettings = false;
+    }
+  }
+
+  async function saveYoutubeSettings() {
+    if (savingYtSettings) return;
+    savingYtSettings = true;
+    error = null;
+    success = null;
+    try {
+      const resp = await apiFetch("/api/youtube/settings", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({
+          resolution: selectedResolution,
+          onlyAudio
+        })
+      });
+      const data = await resp.json().catch(() => ({}));
+      if (!resp.ok || !data?.ok) {
+        throw new Error(data?.error || `HTTP ${resp.status}`);
+      }
+      success = "YouTube indirme ayarları kaydedildi.";
+    } catch (err) {
+      error = err?.message || "YouTube ayarları kaydedilemedi.";
+    } finally {
+      savingYtSettings = false;
+    }
+  }
+
   onMount(() => {
     loadCookies();
+    loadYoutubeSettings();
   });
 
   function formatDate(ts) {
@@ -98,6 +146,47 @@
   </div>
 
   {#if activeTab === "youtube"}
+    <div class="card">
+      <div class="card-header">
+        <div class="title">
+          <i class="fa-solid fa-circle-down"></i>
+          <span>YouTube Download</span>
+        </div>
+      </div>
+
+      <div class="field inline compact left-align">
+        <div class="inline-field">
+          <label for="resolution">Çözünürlük</label>
+          <select
+            id="resolution"
+            bind:value={selectedResolution}
+            disabled={loadingYtSettings || savingYtSettings}
+          >
+            {#each resolutionOptions as res}
+              <option value={res}>{res}</option>
+            {/each}
+          </select>
+        </div>
+        <label class="checkbox-row">
+          <input
+            type="checkbox"
+            bind:checked={onlyAudio}
+            disabled={loadingYtSettings || savingYtSettings}
+          />
+          <span>Only Audio (sadece ses indir)</span>
+        </label>
+      </div>
+
+      <div class="actions">
+        <button class="btn" on:click={loadYoutubeSettings} disabled={loadingYtSettings || savingYtSettings}>
+          <i class="fa-solid fa-rotate"></i> Yenile
+        </button>
+        <button class="btn primary" on:click={saveYoutubeSettings} disabled={loadingYtSettings || savingYtSettings}>
+          <i class="fa-solid fa-floppy-disk"></i> Kaydet
+        </button>
+      </div>
+    </div>
+
     <div class="card">
       <div class="card-header">
         <div class="title">
@@ -238,6 +327,46 @@
     font-weight: 600;
   }
 
+  .field.inline {
+    display: flex;
+    align-items: center;
+    gap: 16px;
+    flex-wrap: wrap;
+  }
+
+  .field.inline.compact {
+    align-items: flex-end;
+  }
+
+  .field.inline.left-align {
+    flex-direction: column;
+    align-items: flex-start;
+    justify-content: flex-start;
+    gap: 10px;
+  }
+
+  .inline-field {
+    display: flex;
+    flex-direction: column;
+    gap: 6px;
+  }
+
+  .field select {
+    min-width: 180px;
+    max-width: 240px;
+    padding: 8px 10px;
+    border: 1px solid var(--border, #dcdcdc);
+    border-radius: 8px;
+    background: #fff;
+  }
+
+  .checkbox-row {
+    display: inline-flex;
+    align-items: center;
+    gap: 8px;
+    font-weight: 600;
+  }
+
   .field textarea {
     min-height: 180px;
     padding: 10px;
@@ -258,6 +387,16 @@
     justify-content: flex-end;
   }
 
+  .actions.left {
+    justify-content: flex-start;
+  }
+
+  .divider {
+    height: 1px;
+    background: #eee;
+    margin: 6px 0;
+  }
+
   .btn {
     display: inline-flex;
     align-items: center;