Add winner archive, host image upload and live demo data

Deliver the demo-ready feature set and seed data so the live site can be
presented end to end:

- Winner archive: ArchivedWinner domain, admin CRUD endpoints/view/manager
  and public archive surface, backed by AddArchivedWinners migration.
- Host presentation: host image upload and artist name on SiteSettings with
  public image endpoint and supporting migrations.
- Clip submissions: idempotent table-ensure migration plus current-season
  demo clips for review workflows.
- Demo seed data: sponsors, share links and 2025 archived winners, with a
  guarded RemoveDemoSeasons cleanup; all seeds guard against real data.
- EnsureRuntimeSchemaParity migration to align runtime schema defensively.
- Admin/home UI refinements; remove unused team role permissions modal and
  dead share-quick-links code.

All seed and schema migrations are idempotent (IF NOT EXISTS / ON CONFLICT)
and skip when real season data is present.

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

docs/ARCHITECTURE.md

@@ -135,7 +135,7 @@ and smaller Vue files split by feature.
 
 | Data | Owner | Notes |
 | --- | --- | --- |
-| Seasons, categories, candidates, winners | Backend | Public and admin views read from canonical backend state. |
+| Seasons, categories, candidates, winners, archived winners | Backend | Public and admin views read from canonical backend state; historical archive winners are managed separately from current season winner publication. |
 | Nominations and clip submissions | Backend | Public writes are validated and reviewed through admin workflows. |
 | Site settings, landing content, footer links, showacts, sponsors | Backend | Content hub/admin settings own public presentation data. |
 | Team members, roles, permissions, sessions | Backend | UI may hide controls, but API authorization is authoritative. |