docs: point onboarding at the dashboard; drop 3 phantom keys from the seeded default (#147)

* fix(entrypoint): drop three phantom history keys from the seeded default

The config written on first boot -- what EVERY fresh Docker install starts
from -- seeded three keys that do not exist on HistoryConfig and are
silently discarded on load:

    auto_cleanup: true
    cleanup_interval_hours: 24
    max_age_days: 30

HistoryConfig has only `database`, `max_messages_per_user`, and
`conversation_timeout`.

To be precise about the impact: history cleanup DOES work -- cleanup_expired()
is wired at main.py:237 and _prune_history() honours max_messages_per_user.
What never existed is the time-based retention model these keys describe (a
30-day age cutoff on a 24h interval). An operator setting max_age_days: 90
expecting 90-day retention was silently ignored.

Not implemented here -- whether time-based retention should exist is a
product decision, not a cleanup. This only stops the default config
promising it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs: point onboarding at the dashboard, not the legacy example config

The documented setup path was `cp config.example.yaml config.yaml`, but that
file is ~40% incomplete: of the 20 top-level Config fields it covers 15,
omitting coverage (the universal bbox), danger_zones, generic_sources,
meshcore_context, commands, and the current notification model
(toggles/destinations/region_routes). Its own notifications header still says
the schema "will be replaced in v0.3 by the 8-toggle model" -- which shipped
long ago. Anyone following the project's own instructions landed on a
degraded surface with no signal a richer config existed.

It is also read by NOTHING at runtime: docker-entrypoint.sh sets
MESHAI_CONFIG=/data/config.yaml and writes its own inline default on first
boot. The Dockerfile still COPYs config.example.yaml into the image, so it is
kept and now labelled reference-only rather than a starting point.

- README: Docker quick-start seeds itself; configure via the dashboard. The
  pip path still uses config.example.yaml (nothing seeds one there) but now
  carries an honest note that it is a minimal bootstrap, not a reference.
  Adds an Advanced section for the split /data/config/ layout and the
  migrate_config_v03 path into it.
- docker-compose.yml: the comment claimed config lives at /data/config.yaml
  as though that were the only layout; corrected to describe both, and note
  secrets live in /data/secrets/.env.
- Dockerfile: document why config.example.yaml is still shipped.

Not done deliberately: config.example.yaml is NOT expanded to cover all 20
sections. A second hand-maintained schema is what caused this drift; the
dashboard is the authoritative surface. The legacy single-file loader is
untouched and still fully supported.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(readme): move dashboard-first onboarding rewrite to root README

work/README.md is about to become a symlink to root README.md on
docs/single-readme. Retarget the Docker/dashboard-first quick start
and config.example.yaml honesty note added in be867d23 from
work/README.md to root README.md, adapted to the root file's own
Quick start structure (cd meshai/work, /work/-prefixed curl URLs), so
none of it is silently dropped when that symlink lands.

---------

Co-authored-by: Matt Johnson <mj@k7zvx.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

work/Dockerfile

@@ -72,6 +72,10 @@ COPY --chown=meshai:meshai meshai/ ./meshai/
 COPY --from=frontend --chown=meshai:meshai /build/meshai/dashboard/static/ ./meshai/dashboard/static/
 COPY --chown=meshai:meshai pyproject.toml .
 COPY --chown=meshai:meshai README.md .
+# Reference only: docker-entrypoint.sh writes its own minimal default to
+# /data/config.yaml on first boot and does NOT read this file. It's shipped
+# for local/pip installs and anyone who wants the legacy single-file schema
+# on hand inside the container (e.g. via `docker compose exec`).
 COPY --chown=meshai:meshai config.example.yaml .
 COPY --chown=meshai:meshai docker-entrypoint.sh .