docs: document async generation, optional sign-in, data control and refresh counts

[upgradedev]

Summary

Brings the judge-facing docs up to date with the five PRs that landed this
week (#33 through #38: Firebase ID-token verification, async submit + poll
job store and its frontend wiring, optional per-user multitenancy, and the
concurrency load test) and reconciles stale test counts. Docs only, no
source or test changes.

• README.md: extends the API endpoints list with the four new routes;
  adds "Async generation (submit + poll)" and "Optional accounts (Google
  sign-in)" sections next to Architecture; adds a "Your photos and your
  data" section after PII safety (what leaves the browser in live mode,
  no captioning/vision step, self-service control, provider-retention
  disclaimer); refreshes the Testing & CI counts.
• frontend/README.md: fixes two now-stale claims ("POST /reels is
  synchronous (no polling)" and the wizard's Generate step both predate the
  async submit+poll wiring) and documents the Authorization header
  attachment.
• demo/SUBMISSION.md: refreshes the stale 2026-07-24 test counts, adds
  firebase-auth to "Built with", and adds one bullet under Production
  readiness for the async job + accounts work.
• demo/STATE.md: adds a new canonical dated entry (2026-07-29)
  superseding the 2026-07-24 one (marked accordingly, kept for history),
  and updates the Production Readiness scorecard cell in place (same
  pattern the 2026-07-24 PR used).

Claims verified against code before writing

• Async submit (202 + job_id) / poll (queued/running/done/failed)
  and the in-process-worker honest limitation: src/cinemory/jobs.py,
  src/cinemory/api.py (create_reel_job, get_reel_job, _run_job).
• Frontend now submits + polls for every real-photo generation:
  frontend/src/components/steps/GenerateReel.tsx (uses
  useSubmitReelJob + usePollReelJob, not the old multipart upload).
• Guest-only default, no sign-in UI, Firebase SDK never fetched when the
  four VITE_FIREBASE_* vars are unset: frontend/src/lib/auth.ts
  (isAuthEnabled), frontend/src/components/AuthMenu.tsx (if (!isAuthEnabled()) return null).
• Backend verifies the Firebase ID token itself (Google's public certs, no
  Admin SDK, no service-account secret): src/cinemory/auth.py; confirmed
  no firebase-admin dependency in requirements.txt / pyproject.toml.
• Structural per-tenant isolation, /me/library, /me/data, tenant id
  only from the verified token: src/cinemory/api.py
  (get_tenant, _TenantScopedStorage, get_my_library,
  delete_my_data).
• Concurrency test proving isolation under load:
  tests/integration/test_load.py::test_concurrent_multitenant_isolation_under_load.
• Photos land in the private B2 bucket and the provider fetches them via a
  1-hour presigned URL (live mode only):
  src/cinemory/adapters/genblaze_provider.py (_external_inputs,
  _INPUT_URL_EXPIRES_SECS = 3600); offline mode never talks to B2 (fakes
  only).
• No captioning/vision step: src/cinemory/ingest.py builds each prompt
  from a fixed 5-entry rotation of camera-movement phrases blended with the
  occasion preset (occ.style_prompt(prompts[c % len(prompts)])), never
  from photo content; pipeline.py only ever calls the provider with
  Modality.VIDEO. Grepped the whole src/cinemory tree for
  caption/vision/describe/BLIP-style terms; the only hit was an unrelated
  LinkedIn API field (uploadCaptions).
• Test counts: read from the latest green CI run on main
  (30448211424,
  commit a07c0a3): backend 314 passed + 4 skipped (unit 156+1, integration
  99+3, e2e 59), pen-test 62 passed, frontend 280 vitest tests across 39
  files.

Test plan

• Verified every claim above against the actual merged code (see list).
• Confirmed both Mermaid diagrams in README.md are untouched (diff only
  adds new sections around them).
• Confirmed the three README image references are still git-tracked.
• Grepped the diff for em-dash / en-dash-as-em in every line I added;
  none introduced (pre-existing dashes in untouched surrounding text
  were left alone).
• Confirmed scripts/readiness.py (the CI readiness gate) has no
  dependency on README/SUBMISSION/STATE content.
• CI green on all jobs (polling after opening this PR).