fix(infra): install pgvector and uuid-ossp extensions in mosaic-db-init

Mosaic Stack API schema requires both vector (pgvector) and uuid-ossp
extensions. The mosaic user cannot CREATE EXTENSION (requires superuser),
so extensions must be installed by the admin user during db-init before
Prisma runs migrations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/prisma/migrations/20260303000001_ms21_user_auth_fields/migration.sql

@@ -1,13 +0,0 @@
--- MS21: Add admin, local auth, and invitation fields to users table
--- These columns were added to schema.prisma but never captured in a migration.
-
-ALTER TABLE "users"
-  ADD COLUMN IF NOT EXISTS "deactivated_at" TIMESTAMPTZ,
-  ADD COLUMN IF NOT EXISTS "is_local_auth" BOOLEAN NOT NULL DEFAULT false,
-  ADD COLUMN IF NOT EXISTS "password_hash" TEXT,
-  ADD COLUMN IF NOT EXISTS "invited_by" UUID,
-  ADD COLUMN IF NOT EXISTS "invitation_token" TEXT,
-  ADD COLUMN IF NOT EXISTS "invited_at" TIMESTAMPTZ;
-
--- CreateIndex
-CREATE UNIQUE INDEX IF NOT EXISTS "users_invitation_token_key" ON "users"("invitation_token");