feat: Hybride Passkey-Freigabe für Skipper und Crew

Skipper (nur Owner) und Crew (WRITE-Collaborators) können Logbuchseiten
optional per WebAuthn freigeben; klassische Unterschrift bleibt als Fallback.
Signatur ist an den Eintrags-Hash gebunden, Export in CSV/PDF angepasst.

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

server/src/index.ts

@@ -5,6 +5,7 @@ import authRouter from './routes/auth.js'
 import logbooksRouter from './routes/logbooks.js'
 import syncRouter from './routes/sync.js'
 import collaborationRouter from './routes/collaboration.js'
+import signRouter from './routes/sign.js'
 import { prisma } from './db.js'
 
 dotenv.config()
@@ -20,6 +21,7 @@ app.use('/api/auth', authRouter)
 app.use('/api/logbooks', logbooksRouter)
 app.use('/api/sync', syncRouter)
 app.use('/api/collaboration', collaborationRouter)
+app.use('/api/sign', signRouter)
 
 // Health check endpoint
 app.get('/api/health', async (req, res) => {