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/main.ts

@@ -0,0 +1,43 @@
+import { i18n } from './i18n'
+import { sdk } from './sdk'
+import { uiPort } from './utils'
+
+/**
+ * Main daemon definition.
+ *
+ * Mounts the `main` volume at /data (same contract as 0.3.5) and runs the
+ * container's ENTRYPOINT (docker_entrypoint.sh -> Next.js standalone).
+ *
+ * Readiness: we check the listening port rather than hitting /api/health
+ * because the Next.js server starts listening before Prisma has warmed up;
+ * the entrypoint's own DB seeding logic is responsible for DB readiness.
+ * If you want a stricter gate later, switch to `sdk.healthCheck.checkWebUrl`
+ * pointed at `http://localhost:3000/api/health` and look for `status: ok`.
+ */
+export const main = sdk.setupMain(async ({ effects }) => {
+  console.info(i18n('Starting Proof of Work'))
+
+  return sdk.Daemons.of(effects).addDaemon('main', {
+    subcontainer: await sdk.SubContainer.of(
+      effects,
+      { imageId: 'main' },
+      sdk.Mounts.of().mountVolume({
+        volumeId: 'main',
+        subpath: null,
+        mountpoint: '/data',
+        readonly: false,
+      }),
+      'proof-of-work-main',
+    ),
+    exec: { command: sdk.useEntrypoint() },
+    ready: {
+      display: i18n('Web Interface'),
+      fn: () =>
+        sdk.healthCheck.checkPortListening(effects, uiPort, {
+          successMessage: i18n('The web interface is ready'),
+          errorMessage: i18n('The web interface is not ready'),
+        }),
+    },
+    requires: [],
+  })
+})