Merge branch 'fix/deploy-unattended-blockers' into main

Two independent lines of production hardening diverged at 7d0334b and attacked
overlapping problems. Neither was a superset, so this is a merge of substance
rather than a fast-forward: every conflict was resolved on the merits, and the
losing side's intent was re-checked against the winner rather than assumed.

MIGRATIONS. The branch's 021/022/023 collided with main's already-DEPLOYED
021_hashtag_counts_respect_bans and 022_client_upload_idempotency. Renumbered to
023/024/025 in a prior commit — main's versions are applied in production, so
their version numbers are immutable and the branch's had to move. Verified by
running the full sqlx::test suite, which applies the whole chain from scratch.

RESOLVED IN MAIN'S FAVOUR (the branch would have regressed these):
  * upload-queue.ts wholesale — the branch's copy has ZERO client_upload_id
    references, so taking it would have silently destroyed end-to-end upload
    idempotency, the one thing standing between a lost response and a duplicate
    photo charged twice against the guest's quota.
  * maintenance.rs supervisor — the branch replaced it with a bare tokio::spawn,
    where one panic silently stops session pruning, media reclaim, the temp
    sweep and both HashMap prunes, permanently and with no log line.
  * The decode-budget probe on spawn_blocking, not inline on the async runtime.
  * feed/+page.svelte's 8s debounce + jitter + max-wait + hidden-tab deferral,
    against the branch's naive 800ms — at 100 guests the branch's version walks
    straight into the per-user feed rate limit.
  * db.rs pool tuning, /uploaders, and the docker-compose deployment story.
  * ONE /health, still DB-backed. The branch's split (dependency-free liveness +
    DB-backed readiness) is defensible, but a constant-"ok" /health is the exact
    defect faea555 fixed and verified live, its motive (Caddy's boot gate) is
    already covered by app depends_on db: service_healthy, and the two handlers
    were the same SELECT 1 under two names.

TAKEN FROM THE BRANCH:
  * The large-PNG OOM guard and its bounded-retry counter (023). Together these
    turn a single upload that can OOM-kill a 1G container into a bounded failure
    instead of an infinite restart loop under `restart: unless-stopped`.
  * 024_feed_scalar_counts — the feed no longer aggregates the whole event per
    page. Pure SQL; column names, order and types are unchanged by design.
  * The admin-lockout fix: look the admin up BY ROLE, never by name. 025 also
    frees any guest already squatting on a reserved name.
  * PIN lockout tier ordering, bounded caption/hashtag reads, SSE ticket caps,
    PoolTimedOut -> 503 + Retry-After, and the ffmpeg stderr drain.
  * backfill_video_posters, which main lacked entirely.
  * TempFileGuard, plus sweep_orphan_originals wired into main's SUPERVISED loop
    (not the branch's bare one) — it reclaims final-named originals whose commit
    never happened, a class main's .tmp-only sweep structurally cannot see.
  * shouldAbortForStall, hand-ported into main's upload-queue.ts since that file
    was resolved to main. Widens the watchdog at loadend instead of disarming it,
    bounding a half-open socket at 2 minutes rather than handing the window to
    xhr.timeout (5-60 min) with the whole queue's `processing` latch held.

ALSO: RUST_LOG and EXPORT_PATH pinned in compose. The code fallback was
`debug` (a line per request, all night) and EXPORT_PATH was the one path with a
mount-shaped default that nothing validated.

Verified: cargo check --all-targets, cargo clippy (clean), 144/144 backend tests
against a live Postgres including upload_idempotency and upload_concurrency,
51/51 vitest, svelte-check 0 errors, eslint clean, vite build.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docker-compose.yml

@@ -56,9 +56,24 @@ services:
     logging: *default-logging
     env_file: .env
     environment:
+      # Default to info. Without this the code fallback in main.rs applies, which is
+      # `eventsnap_backend=debug,tower_http=debug` — a line per HTTP request AND per
+      # response, including every preview fetch, for a multi-day run. The x-logging cap
+      # above bounds the disk cost but not the CPU/IO one.
+      #
+      # Set here rather than only in `.env` because a stock deploy sets RUST_LOG nowhere,
+      # and this is the layer an operator will actually find when they need to raise it
+      # for a single event (`RUST_LOG=eventsnap_backend=debug docker compose up -d app`).
+      RUST_LOG: ${RUST_LOG:-info}
       # Activates the production secret guard in config.rs — refuses to boot with
       # placeholder JWT_SECRET / ADMIN_PASSWORD_HASH.
       APP_ENV: production
+      # Pinned beside MEDIA_PATH for the same reason, and because nothing validates it:
+      # config.rs defaults it to /exports but never checks that it is a mount or that it
+      # differs from media_path. A stray EXPORT_PATH in .env builds the keepsake into the
+      # container's writable layer, where it passes every health check and disk preflight
+      # and then evaporates on the next `up -d`.
+      EXPORT_PATH: /exports
       # The media volume is mounted at /media (below), so the app MUST write there.
       # Pin it here rather than trusting .env: if MEDIA_PATH in .env points elsewhere
       # (e.g. a host path used for running the backend natively) the container can't