feat: Rechnungen, Dokumente und Preview im Ticket buendeln

- InvoiceNinja-Rechnungen pro Kunde/Ticket anzeigen, verknuepfen und aus
  Ticket heraus erstellen (integrationsApi, useInvoices, InvoicePanel)
- Paperless-ngx: Ticket-Uploads automatisch synchronisieren und Kunden-/
  Ticket-Dokumente durchsuchen/anzeigen (DocumentsPanel, FileUploadModal)
- Projekt-/Preview-Karte mit Status, Provisioning und letztem Commit
- Einheitliches Ticket-Detail mit Tabs (Details/Arbeitsblaetter/Rechnungen/
  Dokumente/Projekt) + zugehoerige Styles

Aufruf des Integrations-Backends same-origin per Appwrite-JWT.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/integrationsApi.js

@@ -0,0 +1,94 @@
+import { account } from './appwrite'
+
+/**
+ * Client fuer das Integrations-Backend (InvoiceNinja + Paperless).
+ * Same-Origin unter /api/integrations, authentifiziert per Appwrite-JWT.
+ */
+const BASE = '/api/integrations'
+
+async function authHeaders(extra = {}) {
+  const { jwt } = await account.createJWT()
+  return { 'X-Appwrite-JWT': jwt, ...extra }
+}
+
+async function call(path, { method = 'GET', body } = {}) {
+  const headers = await authHeaders(body ? { 'Content-Type': 'application/json' } : {})
+  const res = await fetch(`${BASE}${path}`, {
+    method,
+    headers,
+    body: body ? JSON.stringify(body) : undefined,
+  })
+  const data = await res.json().catch(() => ({}))
+  if (!res.ok) {
+    throw new Error(data.error || `Integrations-Fehler ${res.status}`)
+  }
+  return data
+}
+
+async function callBlob(path) {
+  const headers = await authHeaders()
+  const res = await fetch(`${BASE}${path}`, { headers })
+  if (!res.ok) throw new Error(`Download fehlgeschlagen (${res.status})`)
+  return res.blob()
+}
+
+function qs(params = {}) {
+  const sp = new URLSearchParams()
+  Object.entries(params).forEach(([k, v]) => {
+    if (v !== undefined && v !== null && v !== '') sp.set(k, v)
+  })
+  const s = sp.toString()
+  return s ? `?${s}` : ''
+}
+
+async function openBlobInNewTab(blob) {
+  const url = URL.createObjectURL(blob)
+  window.open(url, '_blank', 'noopener')
+  setTimeout(() => URL.revokeObjectURL(url), 60_000)
+}
+
+export const integrationsApi = {
+  // ---- health ----
+  health: () => call('/health'),
+
+  // ---- InvoiceNinja: clients ----
+  listClients: (search = '') => call(`/clients${qs({ search })}`),
+  createClient: (payload) => call('/clients', { method: 'POST', body: payload }),
+
+  // ---- InvoiceNinja: invoices ----
+  listInvoices: (clientId) => call(`/invoices${qs({ clientId })}`),
+  createInvoice: (payload) => call('/invoices', { method: 'POST', body: payload }),
+  async openInvoicePdf(id) {
+    const blob = await callBlob(`/invoices/${encodeURIComponent(id)}/pdf`)
+    await openBlobInNewTab(blob)
+  },
+
+  // ---- Paperless ----
+  listDocuments: (params = {}) => call(`/paperless/documents${qs(params)}`),
+  ensureCorrespondent: (name) => call('/paperless/ensure-correspondent', { method: 'POST', body: { name } }),
+  ensureTag: (name) => call('/paperless/ensure-tag', { method: 'POST', body: { name } }),
+  uploadToPaperless: (payload) => call('/paperless/upload', { method: 'POST', body: payload }),
+  async openDocument(id, kind = 'preview') {
+    const blob = await callBlob(`/paperless/documents/${encodeURIComponent(id)}/${kind}`)
+    await openBlobInNewTab(blob)
+  },
+}
+
+// InvoiceNinja status_id -> deutsche Bezeichnung + Farbe
+export const INVOICE_STATUS = {
+  1: { label: 'Entwurf', color: '#a0aec0' },
+  2: { label: 'Versendet', color: '#3b82f6' },
+  3: { label: 'Teilzahlung', color: '#f59e0b' },
+  4: { label: 'Bezahlt', color: '#10b981' },
+  5: { label: 'Storniert', color: '#ef4444' },
+  '-1': { label: 'Storniert', color: '#ef4444' },
+}
+
+export function formatMoney(amount, currency = 'EUR') {
+  const n = Number(amount || 0)
+  try {
+    return new Intl.NumberFormat('de-DE', { style: 'currency', currency }).format(n)
+  } catch {
+    return `${n.toFixed(2)} ${currency}`
+  }
+}