Phase 8: CSV + ICS export, print view, MkDocs docs, SBOM + dev-mode auth

Auth (Test-Mode):
  - middleware.AuthMiddleware now takes a devMode flag. In dev,
    requests without Authorization fall back to a deterministic dev
    UUID (00000000-...-001) and role=teacher. ENVIRONMENT=production
    re-enables the strict 401 path.
  - main.go wires devMode = cfg.Environment != "production".
  - page.tsx replaces the red 'Anmeldung noch nicht integriert' banner
    with a softer Testumgebung notice; the manual-token form moves
    behind a nested details block.

Export endpoints (school-service):
  - LoadExportLessons joins tt_lesson with tt_period for wall-clock
    times; one query feeds both CSV and ICS.
  - WriteCSV streams 10 columns including pinned flag.
  - WriteICS emits one VEVENT per lesson anchored to a Monday — caller
    overridable via ?start=YYYY-MM-DD. RFC 5545 escapes for ',', ';',
    '\n' in icsEscape().
  - NextMonday helper for the default anchor.
  - GET /timetable/solutions/:id/export.{csv,ics} handlers attach
    Content-Disposition: attachment so browsers download instead of
    rendering.

Frontend:
  - lib/stundenplan/api.ts downloadSolutionExport() fetches as blob,
    triggers a synthetic <a download> click, and forwards the JWT when
    present.
  - PlanView gains CSV / ICS / Drucken buttons next to the perspective
    selector. The toolbar carries class 'no-print' so window.print()
    yields only the grid.
  - globals.css @media print rule hides chrome, forces white
    background, gives the table proper borders for A4.

Docs:
  - docs-src/services/stundenplan/{index,architecture,constraints,
    solver-tuning,export}.md with nav entry in mkdocs.yml under
    Services → Stundenplaner.
  - sbom/stundenplan/README.md lists manually-verified key dependencies
    and the policy reference. scripts/stundenplan-sbom.sh generates
    full machine-readable inventories via go-licenses + pip-licenses
    + license-checker when those tools are available.

Tests:
  - internal/services/timetable_exports_test.go: 4 unit tests covering
    CSV column layout + quoting, ICS structure + DTSTART formatting,
    icsEscape special chars, NextMonday weekday math.
  - studio-v2/e2e/stundenplan-export.spec.ts split out of the main spec
    file (LOC budget) — 3 tests for button render, CSV download,
    ICS download.
  - mockSchoolApi extended with export.csv + export.ics routes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

studio-v2/lib/stundenplan/api.ts

@@ -160,3 +160,30 @@ export const lessonsApi = {
       body: JSON.stringify({ pinned }),
     }),
 }
+
+// Phase 8: exports. Fetched as blobs through the proxy so the JWT (when
+// set) is forwarded; download is triggered by creating an object URL.
+export async function downloadSolutionExport(
+  solutionId: string,
+  format: 'csv' | 'ics',
+  options: { startDate?: string } = {},
+): Promise<void> {
+  const token = getStundenplanToken()
+  const headers: Record<string, string> = {}
+  if (token) headers['Authorization'] = `Bearer ${token}`
+
+  const qs = format === 'ics' && options.startDate ? `?start=${options.startDate}` : ''
+  const res = await fetch(`/api/school/timetable/solutions/${solutionId}/export.${format}${qs}`, { headers })
+  if (!res.ok) {
+    throw new Error(`Export fehlgeschlagen (HTTP ${res.status})`)
+  }
+  const blob = await res.blob()
+  const url = URL.createObjectURL(blob)
+  const a = document.createElement('a')
+  a.href = url
+  a.download = `stundenplan-${solutionId.slice(0, 8)}.${format}`
+  document.body.appendChild(a)
+  a.click()
+  a.remove()
+  URL.revokeObjectURL(url)
+}