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/e2e/_helpers.ts

@@ -128,6 +128,21 @@ export async function mockSchoolApi(page: Page, opts: MockOpts = {}) {
       body: JSON.stringify({ message: 'ok', pinned: body.pinned ?? false }),
     })
   })
+  // Phase 8: CSV + ICS exports. Routed BEFORE the generic /solutions/:id
+  // catch-all so the .csv / .ics suffix path is matched first.
+  await page.route(/\/api\/school\/timetable\/solutions\/[^/]+\/export\.csv$/, async (route) => {
+    return route.fulfill({
+      status: 200, contentType: 'text/csv',
+      body: 'day_of_week,period_index,start_time,end_time,class,subject,subject_code,teacher,room,pinned\n1,1,08:00,08:45,5a,Mathe,M,"Schmidt, Anna",A101,false\n',
+    })
+  })
+  await page.route(/\/api\/school\/timetable\/solutions\/[^/]+\/export\.ics(\?.*)?$/, async (route) => {
+    return route.fulfill({
+      status: 200, contentType: 'text/calendar',
+      body: 'BEGIN:VCALENDAR\r\nVERSION:2.0\r\nEND:VCALENDAR\r\n',
+    })
+  })
+
   await page.route(/\/api\/school\/timetable\/solutions\/[^/]+$/, async (route) => {
     if (route.request().method() === 'DELETE') {
       return route.fulfill({ status: 200, contentType: 'application/json', body: '{"message":"deleted"}' })