feat: Kundenportal-Ausbau - Tabs, Projekt-Einblicke, Git-Zeiterfassung, Rechnungen, Chat

Kunden-Dashboard:
- Tab-Navigation: Projekte | Was wurde gemacht | Rechnungen | Chat
- Projekt-Details pro Projekt: letzte Git-Commits (Titel+Beschreibung),
  Projektgroesse, Datei-Uebersicht (Top-Level aggregiert), Ticket-Arbeiten
- Rechnungen: gestylte Liste mit Status-Pillen, Ansehen/Zahlen-Link,
  PDF-Download ueber Server-Proxy (IDOR-geschuetzt)
- Chat mit dem Webklar-Team (Polling, Ungelesen-Badge, viewAs blockiert)

Admin-Dashboard:
- Chat-Tab: Konversationsliste + Thread + Antwortfeld, Ungelesen-Badge

Backend:
- giteaAdmin: getRepoInfo, listRepoCommits, getRepoTreeSummary
- projectInsights: 5-min-Cache, Invalidierung per Gitea-Webhook
- /api/projects/:id/git|files|work mit Ownership-Check (404)
- /api/chat/* (Kunde) + /api/portal-admin/chats/* (Admin), portalMessages-Collection
- mailer: E-Mail-Benachrichtigung an Admins bei Kundennachricht (15-min-Throttle)
- gitWorksheet: dd.mm.yyyy, voller Commit-Body, startTime leer (Zeit-Nachtrag),
  Auto-Webpage-Ticket bei Push auf Projekt ohne Ticket (ensureProjectTicket)
- customerActivity: Git-Push-Eintraege fuer Kunden sichtbar

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/services/giteaAdmin.js

@@ -300,6 +300,94 @@ export async function createProjectFromTemplate({
   }
 }
 
+/** Repo-Basisdaten (Groesse in KB, Default-Branch). */
+export async function getRepoInfo(repoFullName) {
+  const [owner, repo] = String(repoFullName || '').split('/')
+  if (!owner || !repo) return null
+  const data = await giteaFetch(`/repos/${owner}/${repo}`)
+  return {
+    sizeKb: Number(data.size || 0),
+    defaultBranch: data.default_branch || 'main',
+    updatedAt: data.updated_at || '',
+    htmlUrl: data.html_url || `${config.gitea.baseUrl}/${repoFullName}`,
+  }
+}
+
+/** Letzte Commits eines Repos (volle Message inkl. Body). */
+export async function listRepoCommits(repoFullName, { branch = 'main', limit = 20 } = {}) {
+  const [owner, repo] = String(repoFullName || '').split('/')
+  if (!owner || !repo) return []
+  // stat/verification/files abschalten - sonst berechnet Gitea Diff-Stats pro Commit
+  const data = await giteaFetch(
+    `/repos/${owner}/${repo}/commits?sha=${encodeURIComponent(branch)}&limit=${limit}&stat=false&verification=false&files=false`
+  )
+  return (Array.isArray(data) ? data : []).map((entry) => ({
+    sha: entry.sha || '',
+    shortSha: (entry.sha || '').slice(0, 7),
+    message: entry.commit?.message || '',
+    authorName:
+      entry.commit?.author?.name || entry.author?.login || entry.committer?.login || 'Unbekannt',
+    date: entry.commit?.author?.date || entry.created || '',
+    url: entry.html_url || `${config.gitea.baseUrl}/${repoFullName}/commit/${entry.sha}`,
+  }))
+}
+
+/**
+ * Datei-Uebersicht: aggregiert den Git-Baum serverseitig nach Top-Level-Eintraegen
+ * (nie den rohen Baum ans Frontend geben - kann tausende Eintraege haben).
+ */
+export async function getRepoTreeSummary(repoFullName, ref = 'main') {
+  const [owner, repo] = String(repoFullName || '').split('/')
+  if (!owner || !repo) return null
+  const data = await giteaFetch(
+    `/repos/${owner}/${repo}/git/trees/${encodeURIComponent(ref)}?recursive=true&per_page=1000`
+  )
+
+  const entries = Array.isArray(data?.tree) ? data.tree : []
+  const topLevelMap = new Map()
+  let totalFiles = 0
+  let totalSizeBytes = 0
+
+  for (const entry of entries) {
+    const isBlob = entry.type === 'blob'
+    const size = isBlob ? Number(entry.size || 0) : 0
+    const path = String(entry.path || '')
+    const slash = path.indexOf('/')
+    const topSegment = slash === -1 ? path : path.slice(0, slash)
+    const isDir = slash !== -1 || entry.type === 'tree'
+
+    if (isBlob) {
+      totalFiles += 1
+      totalSizeBytes += size
+    }
+
+    if (!topSegment) continue
+    const existing = topLevelMap.get(topSegment) || {
+      path: topSegment,
+      type: isDir ? 'dir' : 'file',
+      fileCount: 0,
+      sizeBytes: 0,
+    }
+    if (isDir) existing.type = 'dir'
+    if (isBlob) {
+      existing.fileCount += 1
+      existing.sizeBytes += size
+    }
+    topLevelMap.set(topSegment, existing)
+  }
+
+  const topLevel = [...topLevelMap.values()]
+    .sort((a, b) => b.sizeBytes - a.sizeBytes)
+    .slice(0, 50)
+
+  return {
+    totalFiles,
+    totalSizeBytes,
+    truncated: Boolean(data?.truncated),
+    topLevel,
+  }
+}
+
 const README_CANDIDATES = ['README.md', 'readme.md', 'Readme.md', 'README.MD', 'README']
 
 export async function fetchRepoReadme(repoFullName) {