fix(audit): restore broken upload pipeline + role-based E2E audit fixes

A comprehensive role-based E2E audit (guest/host/admin, across browser
sessions) surfaced one critical and several smaller issues; this addresses
them and hardens the tests that missed them.

Critical
- The client upload pipeline was fully broken: the IndexedDB v1->v2 upgrade
  opened a *new* transaction inside the upgrade callback, which throws during
  a version-change transaction and aborted the whole upgrade, leaving the
  queue object store uncreated -- so no UI upload ever fired. Reuse the
  version-change transaction the callback provides, and bump the DB to v3 with
  a contains() guard so installs already corrupted by the shipped bug
  self-heal on next load. Re-enabled the previously-fixme'd UI upload E2E test.

High / Medium
- Event lock is uploads-only again: likes, comments and browsing stay open
  while the event is locked (USER_JOURNEYS 9.3 / FEATURES) -- it was wrongly
  freezing social interaction. Updated the event-lock spec accordingly.
- get_original now excludes soft-deleted and ban-hidden uploads, and direct
  /media/originals/** serving is blocked, so a hidden user's originals can no
  longer be pulled by UUID (all originals go through the checked alias).
- The upload handler reads the file field with an early-abort size cap chosen
  from the declared content-type, instead of buffering the entire body before
  the size check.

Low
- unban_user mirrors the ban role guard (a host can no longer unban a
  host/admin banned by an admin).
- reset_user_pin's UPDATE is event-scoped.
- Admin login returns and stores a real identity (user_id + display name)
  instead of a blank session.
- The host user list no longer renders target-actions (ban/promote/demote/PIN)
  on the caller's own row, where the backend always rejected them.
- /diashow gains a client-side auth guard like the other protected routes.
- The join page shows the event name via a new public GET /api/v1/event.

Verified: backend cargo build clean, frontend svelte-check 0 errors, full
Playwright E2E suite 144 passed / 1 skipped.

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

backend/src/main.rs

@@ -57,6 +57,7 @@ async fn main() -> Result<()> {
 
     let api = Router::new()
         // Auth
+        .route("/api/v1/event", get(handlers::public::get_public_event))
         .route("/api/v1/join", post(auth::handlers::join))
         .route("/api/v1/recover", post(auth::handlers::recover))
         .route("/api/v1/admin/login", post(auth::handlers::admin_login))
@@ -144,6 +145,16 @@ async fn main() -> Result<()> {
     let router = Router::new()
         .route("/health", get(|| async { "ok" }))
         .merge(api)
+        // Block direct HTTP access to originals. They live under `media_path` (so the
+        // compression worker and export can read them off disk) but must NOT be pullable
+        // straight from `/media/originals/**` — that would bypass the visibility checks in
+        // `get_original` (soft-delete + ban-hide). Every legitimate original fetch goes
+        // through `/api/v1/upload/{id}/original`; previews/thumbnails under `/media` stay
+        // public. The more specific nest takes precedence over `/media` below.
+        .nest_service(
+            "/media/originals",
+            get(|| async { axum::http::StatusCode::NOT_FOUND }),
+        )
         .nest_service("/media", media_service)
         .layer(TraceLayer::new_for_http())
         .with_state(state);