feat(client-groups): CM-1 data layer — groups entity, membership, service, Mailchimp scaffold

- client_groups + client_group_members tables (migration 0094, port_id cascade)
- client_groups permission resource (view/manage) in catalog + role backfill
- service: CRUD + wipe-and-rewrite membership + member email resolution
- mailchimp.service scaffold: config reader + inert one-way sync (mapping
  deferred until the client's MC account is wired, per CM-1 decision)
- 4 integration tests (CRUD, membership, email resolution, port-scope guard)

Backend only — API routes + UI to follow. tsc clean, 1635 vitest pass.

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

src/lib/db/schema/client-groups.ts

@@ -0,0 +1,73 @@
+/**
+ * Client groups (CM-1) - first-class mailing/segment groups for clients.
+ *
+ * A `client_groups` row is a named, per-port group (e.g. a mailing list).
+ * `client_group_members` is the M2M join to `clients`. Membership carries its
+ * own `port_id` for defense-in-depth tenant isolation (same doctrine as the
+ * document-folders aggregated projection - port_id at every join).
+ *
+ * Optional Mailchimp mapping lives on the group row: `mailchimpTag` is the
+ * tag/segment name pushed to the port's single Mailchimp audience. Null until
+ * an admin wires Mailchimp up (the integration is inert without creds).
+ */
+
+import { sql } from 'drizzle-orm';
+import { index, pgTable, primaryKey, text, timestamp, uniqueIndex } from 'drizzle-orm/pg-core';
+
+import { clients } from './clients';
+import { ports } from './ports';
+
+export const clientGroups = pgTable(
+  'client_groups',
+  {
+    id: text('id')
+      .primaryKey()
+      .$defaultFn(() => crypto.randomUUID()),
+    portId: text('port_id')
+      .notNull()
+      .references(() => ports.id, { onDelete: 'cascade' }),
+    name: text('name').notNull(),
+    description: text('description'),
+    /** Chip color in the CRM UI. */
+    color: text('color').notNull().default('#6B7280'),
+    /** CM-1 Mailchimp: the tag/segment name this group maps to in the port's
+     *  single Mailchimp audience. Null = not synced. */
+    mailchimpTag: text('mailchimp_tag'),
+    archivedAt: timestamp('archived_at', { withTimezone: true }),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+    updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+  },
+  (table) => [
+    index('idx_client_groups_port').on(table.portId),
+    // Per-port, case-insensitive name uniqueness among non-archived groups.
+    uniqueIndex('idx_client_groups_port_name')
+      .on(table.portId, sql`lower(${table.name})`)
+      .where(sql`${table.archivedAt} IS NULL`),
+  ],
+);
+
+export const clientGroupMembers = pgTable(
+  'client_group_members',
+  {
+    groupId: text('group_id')
+      .notNull()
+      .references(() => clientGroups.id, { onDelete: 'cascade' }),
+    clientId: text('client_id')
+      .notNull()
+      .references(() => clients.id, { onDelete: 'cascade' }),
+    portId: text('port_id')
+      .notNull()
+      .references(() => ports.id, { onDelete: 'cascade' }),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  },
+  (table) => [
+    primaryKey({ columns: [table.groupId, table.clientId] }),
+    index('idx_cgm_client').on(table.clientId),
+    index('idx_cgm_port').on(table.portId),
+  ],
+);
+
+export type ClientGroup = typeof clientGroups.$inferSelect;
+export type NewClientGroup = typeof clientGroups.$inferInsert;
+export type ClientGroupMember = typeof clientGroupMembers.$inferSelect;
+export type NewClientGroupMember = typeof clientGroupMembers.$inferInsert;