Stundenplan Phase 3c: complete Stammdaten + RegelnHub with 4 editors

Frontend additions in studio-v2:
  - PeriodsManager renders the weekly grid as a Mo–So table with one
    row per period_index. New entries auto-increment period_index so
    the user can hit Anlegen repeatedly for a full day's slots.
  - CurriculumManager joins classes + subjects; new entries refuse to
    open when either prerequisite list is empty (banner instead).
  - AssignmentsManager joins teacher × class × subject with the same
    prerequisite-banner pattern.
  - regeln/RegelnHub: vertical sidebar grouping all 15 constraint
    types by parent entity (Lehrer/Fach/Klasse/Raum). Implemented
    editors are clickable, the other 11 are visibly disabled with
    a 'soon' tag.
  - Three new editors:
      TeacherUnavailableWindowEditor (time-window pattern),
      SubjectMaxConsecutiveEditor (number-input pattern),
      SubjectPreferredPeriodEditor (number range pattern).
  - page.tsx wires every tab to its manager; the not-implemented
    placeholder is gone (no more empty tabs).

Test coverage:
  - e2e/stundenplan.spec.ts rewritten: 23 tests across 7 suites,
    covering all 8 tabs, the new managers' prerequisite banners,
    sub-tab switching in the RegelnHub, and the disabled state of
    not-yet-implemented constraint rules. Each test mocks the
    backend via page.route() so the suite stays hermetic.

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

studio-v2/app/stundenplan/page.tsx

@@ -9,7 +9,10 @@ import { KlassenManager } from './_components/KlassenManager'
 import { LehrerManager } from './_components/LehrerManager'
 import { FaecherManager } from './_components/FaecherManager'
 import { RaeumeManager } from './_components/RaeumeManager'
-import { TeacherUnavailableDayEditor } from './_components/regeln/TeacherUnavailableDayEditor'
+import { PeriodsManager } from './_components/PeriodsManager'
+import { CurriculumManager } from './_components/CurriculumManager'
+import { AssignmentsManager } from './_components/AssignmentsManager'
+import { RegelnHub } from './_components/regeln/RegelnHub'
 import { setStundenplanToken, getStundenplanToken } from '@/lib/stundenplan/api'
 
 type Tab = 'klassen' | 'lehrer' | 'faecher' | 'raeume' | 'periods' | 'curriculum' | 'assignments' | 'regeln'
@@ -109,20 +112,10 @@ export default function StundenplanPage() {
           {tab === 'lehrer' && <LehrerManager />}
           {tab === 'faecher' && <FaecherManager />}
           {tab === 'raeume' && <RaeumeManager />}
-          {tab === 'regeln' && <TeacherUnavailableDayEditor />}
-          {(tab === 'periods' || tab === 'curriculum' || tab === 'assignments') && (
-            <div
-              className={`rounded-2xl border backdrop-blur-xl p-8 text-center ${
-                isDark ? 'bg-white/5 border-white/10 text-white/60' : 'bg-white/80 border-black/10 text-slate-500'
-              }`}
-              data-testid="not-implemented"
-            >
-              <p className="text-lg">Noch nicht implementiert: {TABS.find(t => t.id === tab)?.label}</p>
-              <p className="text-sm mt-2">
-                Folgt dem gleichen Muster wie Klassen / Lehrer / Faecher / Raeume.
-              </p>
-            </div>
-          )}
+          {tab === 'periods' && <PeriodsManager />}
+          {tab === 'curriculum' && <CurriculumManager />}
+          {tab === 'assignments' && <AssignmentsManager />}
+          {tab === 'regeln' && <RegelnHub />}
         </section>
       </main>
     </div>