Align backend with frontend, make clips end-to-end, polish admin

Backend
- Add ClipSubmission entity + table (runtime bootstrapper) and
  POST /api/public/clips (server-derives platform from the link)
- Surface clip submissions in the admin season detail
- Add DELETE candidate/category/clip endpoints with audit entries

Frontend
- Clips admin: real moderation view (list, open link, delete) instead
  of placeholder; wired clipSubmissions through types/api/store
- Categories admin: add delete with confirm modal (matches Candidates)
- Voting ranking bar uses the unified purple gradient
- Fix ASCII transliterations to proper German umlauts across admin
- Remove orphan AdminView 2.vue

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/api.ts

@@ -112,6 +112,8 @@ export const api = {
     sendDelete<{ deleted: boolean; candidateId: number }>(`/api/admin/candidates/${candidateId}`),
   deleteAdminCategory: (categoryId: number) =>
     sendDelete<{ deleted: boolean; categoryId: number }>(`/api/admin/categories/${categoryId}`),
+  deleteAdminClip: (clipId: number) =>
+    sendDelete<{ deleted: boolean; clipId: number }>(`/api/admin/clips/${clipId}`),
   approveAdminNomination: (nominationId: number, payload: ApproveNominationPayload) =>
     sendJson<{ saved: boolean; nominationId: number; candidateId: number; created: boolean }>(
       `/api/admin/nominations/${nominationId}/approve`,