fix(live-log): prevent freeze without GPS and prompt for day-start position

Harden geolocation with watchdog timeouts and permission checks so
desktop browsers without GPS no longer hang Live-Log. Show a hint to
log a position when none exists for the day.

Return 503 when crew-pool Prisma models are missing instead of crashing.

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

server/src/utils/crewPoolSchema.ts

@@ -0,0 +1,25 @@
+import { prisma } from '../db.js'
+
+/** Prisma client includes delegates only after `npx prisma generate` on the current schema. */
+export function hasCrewPoolPrismaModels(): boolean {
+  const client = prisma as unknown as {
+    personPayload?: { findMany: unknown }
+    logbookCrewSelectionPayload?: { findUnique: unknown }
+  }
+  return (
+    typeof client.personPayload?.findMany === 'function' &&
+    typeof client.logbookCrewSelectionPayload?.findUnique === 'function'
+  )
+}
+
+export const CREW_POOL_MIGRATION_HINT =
+  'Crew-Pool-Datenbank fehlt. Im Ordner server ausführen: npx prisma generate && npx prisma db push — danach Server neu starten.'
+
+export function isMissingPrismaTable(error: unknown): boolean {
+  return (
+    typeof error === 'object' &&
+    error !== null &&
+    'code' in error &&
+    (error as { code: string }).code === 'P2021'
+  )
+}