feat(downloader): tier-limited classification, config defaults, yt-dlp support

- Classify Patreon "Not allowed to view post" warnings as TIER_LIMITED so
  subscription-gated runs are distinguished from genuine failures, and persist
  error_type/message on completed runs so the distinction survives to the UI.
- Fold PLATFORM_DEFAULTS into _get_default_config so gallery-dl.conf is a
  complete, editable document; _build_config_for_source now preserves the
  user's conf and only re-seeds missing platform sections.
- Add Reset-to-Defaults action in Settings (vs. Revert Changes which just
  reloads disk); show info banner when no gallery-dl.conf exists yet.
- Fix Discord embeds option: must be "all" string, not bool (gallery-dl
  iterates the value).
- Install yt-dlp + ffmpeg in Docker images so Patreon/Mux HLS video posts
  download instead of logging "Cannot import yt-dlp" and skipping.
- Recognize yt-dlp import failures as per-item errors so they don't mask
  TIER_LIMITED/NO_NEW_CONTENT classification.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/stores/settings.js

@@ -27,7 +27,7 @@ export const useSettingsStore = defineStore('settings', () => {
   async function fetchGalleryDLConfig() {
     const response = await settingsApi.getGalleryDL()
     galleryDLConfig.value = response.data.config
-    return response.data.config
+    return response.data
   }
 
   async function updateGalleryDLConfig(config) {
@@ -36,6 +36,12 @@ export const useSettingsStore = defineStore('settings', () => {
     return response.data.config
   }
 
+  async function resetGalleryDLConfig() {
+    const response = await settingsApi.resetGalleryDL()
+    galleryDLConfig.value = response.data.config
+    return response.data.config
+  }
+
   return {
     settings,
     galleryDLConfig,
@@ -44,5 +50,6 @@ export const useSettingsStore = defineStore('settings', () => {
     updateSettings,
     fetchGalleryDLConfig,
     updateGalleryDLConfig,
+    resetGalleryDLConfig,
   }
 })

frontend/src/views/Settings.vue

@@ -184,6 +184,16 @@
           Invalid configuration may cause downloads to fail.
         </v-alert>
 
+        <v-alert
+          v-if="configIsDefault"
+          type="info"
+          variant="tonal"
+          class="mb-4"
+          density="compact"
+        >
+          No gallery-dl.conf found on disk. Showing computed defaults — click Save Configuration to persist.
+        </v-alert>
+
         <v-textarea
           v-model="galleryDLConfigText"
           label="gallery-dl.conf (JSON)"
@@ -205,12 +215,20 @@
           Documentation
         </v-btn>
         <v-spacer />
+        <v-btn
+          variant="text"
+          color="warning"
+          @click="resetConfigDialog = true"
+          :disabled="savingConfig"
+        >
+          Reset to Defaults
+        </v-btn>
         <v-btn
           variant="text"
           @click="loadGalleryDLConfig"
           :disabled="savingConfig"
         >
-          Reset
+          Revert Changes
         </v-btn>
         <v-btn
           color="primary"
@@ -223,6 +241,27 @@
       </v-card-actions>
     </v-card>
 
+    <v-dialog v-model="resetConfigDialog" max-width="500">
+      <v-card>
+        <v-card-title>Reset to Defaults?</v-card-title>
+        <v-card-text>
+          This overwrites gallery-dl.conf with computed defaults, replacing any
+          customizations. Use this to recover after misconfiguring the file.
+        </v-card-text>
+        <v-card-actions>
+          <v-spacer />
+          <v-btn variant="text" @click="resetConfigDialog = false">Cancel</v-btn>
+          <v-btn
+            color="warning"
+            :loading="resettingConfig"
+            @click="resetGalleryDLConfigToDefaults"
+          >
+            Reset
+          </v-btn>
+        </v-card-actions>
+      </v-card>
+    </v-dialog>
+
     <!-- Platform Default Settings -->
     <v-card class="mb-6">
       <v-card-title>
@@ -414,6 +453,9 @@ const savingConfig = ref(false)
 const settings = ref({})
 const galleryDLConfigText = ref('')
 const configError = ref('')
+const configIsDefault = ref(false)
+const resetConfigDialog = ref(false)
+const resettingConfig = ref(false)
 const platforms = ref({})
 const apiHealthy = ref(true)
 const showApiKey = ref(false)
@@ -492,8 +534,9 @@ async function saveSettings() {
 
 async function loadGalleryDLConfig() {
   try {
-    const config = await settingsStore.fetchGalleryDLConfig()
-    galleryDLConfigText.value = JSON.stringify(config, null, 2)
+    const data = await settingsStore.fetchGalleryDLConfig()
+    galleryDLConfigText.value = JSON.stringify(data.config, null, 2)
+    configIsDefault.value = data.is_default === true
     configError.value = ''
   } catch (error) {
     notifications.error(`Failed to load config: ${error.message}`)
@@ -516,6 +559,7 @@ async function saveGalleryDLConfig() {
   try {
     const config = JSON.parse(galleryDLConfigText.value)
     await settingsStore.updateGalleryDLConfig(config)
+    configIsDefault.value = false
     notifications.success('Gallery-dl configuration saved')
   } catch (error) {
     notifications.error(`Failed to save: ${error.message}`)
@@ -524,6 +568,22 @@ async function saveGalleryDLConfig() {
   }
 }
 
+async function resetGalleryDLConfigToDefaults() {
+  resettingConfig.value = true
+  try {
+    const config = await settingsStore.resetGalleryDLConfig()
+    galleryDLConfigText.value = JSON.stringify(config, null, 2)
+    configIsDefault.value = false
+    configError.value = ''
+    resetConfigDialog.value = false
+    notifications.success('Gallery-dl configuration reset to defaults')
+  } catch (error) {
+    notifications.error(`Failed to reset: ${error.message}`)
+  } finally {
+    resettingConfig.value = false
+  }
+}
+
 async function loadPlatforms() {
   try {
     const response = await platformsApi.list()