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.

sidecar/db/providers/schema.ts

@@ -18,8 +18,7 @@ import { pgTable, uuid, text, boolean, timestamp, index } from 'drizzle-orm/pg-c
  * repo is updated, and refusing a new one on release day is a worse failure than passing it through
  * and letting the vendor answer.
  */
-export const providers = pgTable(
-  'providers',
+export const providers = pgTable('atelier_providers',
   {
     id: uuid('id').primaryKey().defaultRandom(),
 
@@ -50,6 +49,6 @@ export const providers = pgTable(
   },
   (table) => [
     // Resolving a request by model is the hot path: every generation does it once.
-    index('providers_model_idx').on(table.model, table.enabled),
+    index('atelier_providers_model_idx').on(table.model, table.enabled),
   ],
 );