Add first-run setup wizard and file browser for library creation

- On first start (no users in DB), show a setup page in the web UI
  to create the admin account instead of reading credentials from .env
- New public endpoints: GET /api/setup/status, POST /api/setup
- New admin endpoint: GET /api/filebrowser?path=... for directory listing
- FileBrowser modal component with navigation, used in Admin > Libraries
- Remove _seed_admin / _seed_default_library from server startup

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

frontend/src/pages/Admin.tsx

@@ -1,7 +1,8 @@
 import React, { useEffect, useState } from 'react'
-import { Users, Library, Settings, Trash2, Plus, RefreshCw, Loader2, Check, X } from 'lucide-react'
+import { Users, Library, Settings, Trash2, Plus, RefreshCw, Loader2, Check, X, FolderOpen } from 'lucide-react'
 import { getUsers, createUser, deleteUser, getSettings, updateSettings } from '../api/me'
 import { getLibraries, scanLibrary, createLibrary, deleteLibrary } from '../api/libraries'
+import FileBrowser from '../components/common/FileBrowser'
 
 type Tab = 'users' | 'libraries' | 'settings'
 
@@ -119,6 +120,7 @@ function LibrariesPanel() {
   const [loading, setLoading] = useState(true)
   const [scanning, setScanning] = useState<string | null>(null)
   const [showCreate, setShowCreate] = useState(false)
+  const [showBrowser, setShowBrowser] = useState(false)
   const [form, setForm] = useState({ name: '', path: '', mediaType: 'book' })
 
   useEffect(() => { getLibraries().then(setLibraries).finally(() => setLoading(false)) }, [])
@@ -160,10 +162,27 @@ function LibrariesPanel() {
             value={form.name} onChange={(e) => setForm({ ...form, name: e.target.value })}
             className="w-full bg-white/5 border border-white/10 rounded-lg px-3 py-2 text-sm text-white placeholder-gray-500 focus:outline-none focus:ring-1 focus:ring-primary"
           />
-          <input type="text" placeholder="Pfad (z.B. /audiofiles/hörbucher)"
-            value={form.path} onChange={(e) => setForm({ ...form, path: e.target.value })}
-            className="w-full bg-white/5 border border-white/10 rounded-lg px-3 py-2 text-sm text-white placeholder-gray-500 focus:outline-none focus:ring-1 focus:ring-primary"
-          />
+          <div className="flex gap-2">
+            <input type="text" placeholder="Pfad (z.B. /audiofiles)"
+              value={form.path} onChange={(e) => setForm({ ...form, path: e.target.value })}
+              className="flex-1 bg-white/5 border border-white/10 rounded-lg px-3 py-2 text-sm text-white placeholder-gray-500 focus:outline-none focus:ring-1 focus:ring-primary"
+            />
+            <button
+              type="button"
+              onClick={() => setShowBrowser(true)}
+              className="flex items-center gap-1.5 bg-white/5 border border-white/10 px-3 py-2 rounded-lg text-sm text-gray-300 hover:text-white hover:bg-white/10"
+            >
+              <FolderOpen size={14} />
+              Durchsuchen
+            </button>
+          </div>
+          {showBrowser && (
+            <FileBrowser
+              initialPath={form.path || '/'}
+              onSelect={(p) => setForm({ ...form, path: p })}
+              onClose={() => setShowBrowser(false)}
+            />
+          )}
           <select value={form.mediaType} onChange={(e) => setForm({ ...form, mediaType: e.target.value })}
             className="w-full bg-white/5 border border-white/10 rounded-lg px-3 py-2 text-sm text-gray-300 focus:outline-none">
             <option value="book">Hörbücher</option>

frontend/src/pages/Setup.tsx

@@ -0,0 +1,84 @@
+import React, { useState } from 'react'
+import { BookOpen, Loader2, Eye, EyeOff } from 'lucide-react'
+import api from '../api/client'
+
+interface Props {
+  onComplete: () => void
+}
+
+export default function Setup({ onComplete }: Props) {
+  const [username, setUsername] = useState('')
+  const [password, setPassword] = useState('')
+  const [showPwd, setShowPwd] = useState(false)
+  const [loading, setLoading] = useState(false)
+  const [error, setError] = useState('')
+
+  const submit = async (e: React.FormEvent) => {
+    e.preventDefault()
+    setError('')
+    setLoading(true)
+    try {
+      await api.post('/api/setup', { username, password })
+      onComplete()
+    } catch (err: any) {
+      setError(err.response?.data?.detail || 'Fehler beim Anlegen')
+    } finally {
+      setLoading(false)
+    }
+  }
+
+  return (
+    <div className="min-h-screen bg-background flex items-center justify-center p-4">
+      <div className="w-full max-w-sm">
+        <div className="flex items-center justify-center gap-3 mb-3">
+          <BookOpen className="text-primary" size={32} />
+          <h1 className="text-3xl font-bold text-white">Audiolib</h1>
+        </div>
+        <p className="text-center text-gray-400 text-sm mb-8">Erster Start — Admin-Konto anlegen</p>
+
+        <form onSubmit={submit} className="bg-surface rounded-xl p-6 space-y-4">
+          <div>
+            <label className="block text-sm text-gray-400 mb-1">Benutzername</label>
+            <input
+              type="text"
+              value={username}
+              onChange={(e) => setUsername(e.target.value)}
+              className="w-full bg-white/5 border border-white/10 rounded-lg px-3 py-2 text-white placeholder-gray-500 focus:outline-none focus:ring-1 focus:ring-primary"
+              placeholder="admin"
+              autoFocus
+            />
+          </div>
+          <div>
+            <label className="block text-sm text-gray-400 mb-1">Passwort</label>
+            <div className="relative">
+              <input
+                type={showPwd ? 'text' : 'password'}
+                value={password}
+                onChange={(e) => setPassword(e.target.value)}
+                className="w-full bg-white/5 border border-white/10 rounded-lg px-3 py-2 pr-10 text-white placeholder-gray-500 focus:outline-none focus:ring-1 focus:ring-primary"
+                placeholder="••••••••"
+              />
+              <button
+                type="button"
+                onClick={() => setShowPwd(!showPwd)}
+                className="absolute right-3 top-1/2 -translate-y-1/2 text-gray-400 hover:text-white"
+                tabIndex={-1}
+              >
+                {showPwd ? <EyeOff size={16} /> : <Eye size={16} />}
+              </button>
+            </div>
+          </div>
+          {error && <p className="text-red-400 text-sm">{error}</p>}
+          <button
+            type="submit"
+            disabled={loading || !username || !password}
+            className="w-full bg-primary text-black font-semibold py-2.5 rounded-lg hover:bg-primary/80 disabled:opacity-50 disabled:cursor-not-allowed flex items-center justify-center gap-2"
+          >
+            {loading && <Loader2 size={16} className="animate-spin" />}
+            Konto anlegen
+          </button>
+        </form>
+      </div>
+    </div>
+  )
+}