Case-insensitive login, auto-matching after scan, per-library sources

- auth: username lookup is now case-insensitive via func.lower()
- scanner: trigger match_audiobook for each newly found item after scan
- matcher: read match_sources from library settings; refactored to loop
  over configured sources in priority order instead of hardcoded sequence
- schemas/routers: expose matchSources in LibraryOut API response
- Admin UI: pill-toggle for MusicBrainz/Open Library/Google Books per library

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

frontend/src/pages/Admin.tsx

@@ -115,11 +115,17 @@ function UsersPanel() {
   )
 }
 
+const MATCH_SOURCES = [
+  { id: 'musicbrainz', label: 'MusicBrainz' },
+  { id: 'open_library', label: 'Open Library' },
+  { id: 'google_books', label: 'Google Books' },
+]
+
 function LibraryForm({
   initial, onSave, onCancel, title,
 }: {
-  initial: { name: string; path: string; mediaType: string }
-  onSave: (v: { name: string; path: string; mediaType: string }) => Promise<void>
+  initial: { name: string; path: string; mediaType: string; matchSources: string[] }
+  onSave: (v: { name: string; path: string; mediaType: string; matchSources: string[] }) => Promise<void>
   onCancel: () => void
   title: string
 }) {
@@ -161,6 +167,36 @@ function LibraryForm({
         <option value="book">Hörbücher</option>
         <option value="podcast">Podcasts</option>
       </select>
+
+      {form.mediaType === 'book' && (
+        <div>
+          <p className="text-xs text-gray-500 mb-2">Matching-Quellen (Reihenfolge = Priorität)</p>
+          <div className="flex flex-wrap gap-2">
+            {MATCH_SOURCES.map((s) => {
+              const checked = form.matchSources.includes(s.id)
+              return (
+                <button
+                  key={s.id}
+                  type="button"
+                  onClick={() => setForm({
+                    ...form,
+                    matchSources: checked
+                      ? form.matchSources.filter((x) => x !== s.id)
+                      : [...form.matchSources, s.id],
+                  })}
+                  className={`px-3 py-1 rounded-full text-xs border transition-colors ${
+                    checked
+                      ? 'bg-primary/20 border-primary text-primary'
+                      : 'bg-white/5 border-white/10 text-gray-400 hover:text-white'
+                  }`}
+                >
+                  {s.label}
+                </button>
+              )
+            })}
+          </div>
+        </div>
+      )}
       <div className="flex gap-2">
         <button onClick={submit} disabled={!form.name || !form.path || saving}
           className="flex items-center gap-2 bg-primary text-black px-4 py-2 rounded-lg text-sm font-medium disabled:opacity-50">
@@ -190,14 +226,20 @@ function LibrariesPanel() {
     setTimeout(() => setScanning(null), 5000)
   }
 
-  const handleCreate = async (form: { name: string; path: string; mediaType: string }) => {
-    await createLibrary({ name: form.name, folders: [{ fullPath: form.path }], media_type: form.mediaType })
+  const handleCreate = async (form: { name: string; path: string; mediaType: string; matchSources: string[] }) => {
+    await createLibrary({
+      name: form.name, folders: [{ fullPath: form.path }], media_type: form.mediaType,
+      settings: { match_sources: form.matchSources },
+    })
     await reload()
     setShowCreate(false)
   }
 
-  const handleUpdate = async (id: string, form: { name: string; path: string; mediaType: string }) => {
-    await updateLibrary(id, { name: form.name, folders: [{ fullPath: form.path }], media_type: form.mediaType })
+  const handleUpdate = async (id: string, form: { name: string; path: string; mediaType: string; matchSources: string[] }) => {
+    await updateLibrary(id, {
+      name: form.name, folders: [{ fullPath: form.path }], media_type: form.mediaType,
+      settings: { match_sources: form.matchSources },
+    })
     await reload()
     setEditingId(null)
   }
@@ -221,7 +263,7 @@ function LibrariesPanel() {
       {showCreate && (
         <LibraryForm
           title="Neue Bibliothek"
-          initial={{ name: '', path: '', mediaType: 'book' }}
+          initial={{ name: '', path: '', mediaType: 'book', matchSources: ['musicbrainz', 'open_library', 'google_books'] }}
           onSave={handleCreate}
           onCancel={() => setShowCreate(false)}
         />
@@ -234,7 +276,7 @@ function LibrariesPanel() {
               {editingId === lib.id ? (
                 <LibraryForm
                   title={`„${lib.name}" bearbeiten`}
-                  initial={{ name: lib.name, path: lib.folders?.[0]?.fullPath || '', mediaType: lib.mediaType || 'book' }}
+                  initial={{ name: lib.name, path: lib.folders?.[0]?.fullPath || '', mediaType: lib.mediaType || 'book', matchSources: lib.matchSources || ['musicbrainz', 'open_library', 'google_books'] }}
                   onSave={(form) => handleUpdate(lib.id, form)}
                   onCancel={() => setEditingId(null)}
                 />