Rebrand to Proof of Work; multi-user 0.4 package with curated library sync

Repo cleanup
- Add top-level .gitignore (was missing; node_modules, .next, *.s9pk,
  image.tar, seed/data/*.db, log files, etc.) and a root README.
- Delete legacy start9/0.3.5/ package (StartOS 0.3.5 wrapper, no longer
  the deploy target).
- Delete start9-example-packaging/ (template from another project).
- Delete planning docs (START9_PACKAGING_LOG.md, VERSIONING.md,
  STARTOS_0.4_UPGRADE_PROMPT.md, ICON_FILES_INDEX.md, etc.) — info now
  lives in the deploy guide and code comments.
- Drop the standalone Dockerfile, docker-compose.yml, ICON_*, and dev
  log/build artifacts from the app dir.
- Drop the v0.1.0:18/19/20 version files (they belonged to the legacy
  workout-log package and don't apply to the new id).

Rename + new package
- Rename app dir workout-planner/ -> proof-of-work/.
- Rename StartOS package id workout-log -> proof-of-work; the new id
  makes this a brand new StartOS service (clean cutover from the old
  one rather than in-place upgrade).
- Reset version graph; v1.0.0:1 is the seeded cutover release. The
  Dockerfile bakes a one-time /data snapshot and docker_entrypoint.sh
  copies it into the new volume on truly-fresh first boot only (both
  /data/app.db missing AND /data/.seeded absent).
- Move start9/0.4-migration/ -> start9/0.4/; the old start9/0.4/ stub
  is gone.

Curated exercise library (multi-user-aware)
- proof-of-work/prisma/exercises.seed.json is the canonical library
  shipped to every install (164 exercises today, dumped from the live
  snapshot).
- proof-of-work/scripts/sync-library.cjs (npm run sync-library) refreshes
  the JSON from start9/0.4/seed/data/app.db after refresh_seed.sh.
- proof-of-work/prisma/seed.ts now reads from the JSON instead of a
  hardcoded 52-exercise array; runs at Docker build time to seed the
  fallback DB and on first boot for fresh installs.
- proof-of-work/prisma/ensureExerciseLibrary.cjs runs on every container
  boot (from docker_entrypoint.sh) and INSERT OR IGNOREs every library
  entry for every user, keyed on (userId, name). Library updates flow
  to existing installs on package upgrade; user-custom exercises
  (isCustom=true) and any colliding names are never overwritten;
  removed exercises stay on existing installs (additive-only).

Deploy guide (start9/0.4/DEPLOY_040.md)
- Rewritten end-to-end for the workout-log -> proof-of-work cutover:
  refresh_seed, sync-library, build, sideload, verify, rotate creds,
  stop the old service, then post-cutover cleanup release v1.0.0:2.

start9/0.4/startos/index.ts

@@ -0,0 +1,11 @@
+/**
+ * Plumbing. DO NOT EDIT.
+ */
+export { createBackup } from './backups'
+export { main } from './main'
+export { init, uninit } from './init'
+export { actions } from './actions'
+import { buildManifest } from '@start9labs/start-sdk'
+import { manifest as sdkManifest } from './manifest'
+import { versionGraph } from './versions'
+export const manifest = buildManifest(versionGraph, sdkManifest)