officer_db with atelier_ prefixes, like every other plugin

the extraction kept atelier's own postgres database, because the brief said to
when the tables already had rows. the owner reversed it, and the reason is not
tidiness: a plugin that behaves differently from every other plugin is a
plugin nobody can reason about.

the separate database meant a second connection string to set before install,
a second thing to back up, a second thing to get wrong on a new machine, and
failure modes no other plugin shares — none of it bought anything except
avoiding a migration.

four tables now: atelier_collections, atelier_collection_items,
atelier_providers, atelier_generations. index and check constraint names carry
the prefix too — those are global in postgres and are the one thing that would
otherwise collide with another plugin.

db/schema.ts re-exports the definitions rather than duplicating them: they stay
beside the code that queries them in sidecar/db/, and that file exists to be
found by gen-plugin-schemas.

ATELIER_POSTGRES_URL is gone. db.ts reads OFFICERDEV_POSTGRES_URL ?? POSTGRES_URL,
which the platform already sets.

the standalone service's rows are NOT here and nothing depends on them being
here — the old service is still running against the old database, untouched,
and migrating is a separate watched step after this is proven on alpha.

README.md

@@ -30,7 +30,7 @@ talks to). This plugin is a fresh extraction into Officer, not a replacement for
 ## Requirements
 
 - An Officer server, version 1.0.0 or later.
-- A **separate Postgres database**, and its own environment variable: `ATELIER_POSTGRES_URL`. Atelier's
+- A **separate Postgres database**, and its own environment variable: `OFFICERDEV_POSTGRES_URL`. Atelier's
   tables (`generations`, `collections`, `collection_items`, `providers`) do not live in `officer_db` —
   see `PLUGIN.md` for why, and set this before installing. There is no default.
 - An OpenAI API key, set with `bun run secret:set atelier-openai-key`, or configured per-provider in
@@ -40,7 +40,7 @@ talks to). This plugin is a fresh extraction into Officer, not a replacement for
 ## Install
 
 From the Officer marketplace: find Atelier, install. That mounts `/api/atelier` and `/atelier`, starts
-the `officer-atelier` sidecar under PM2, and connects it to whatever `ATELIER_POSTGRES_URL` points at —
+the `officer-atelier` sidecar under PM2, and connects it to whatever `OFFICERDEV_POSTGRES_URL` points at —
 which has to already have the schema (the standalone repo's own `bun db:push` creates it; this plugin
 does not run migrations against a database it does not own the schema of).