fix(communications): create email_templates table + resolve platform_admin brand fallback

Two related bugs caused the 'New Template' modal on
/admin/communications to fail with a database error:

1. The `email_templates` table was defined in `db/schema/marketing.ts`
   (Drizzle) but never migrated, so the modal's `upsertTemplate`
   server action errored with 'relation "email_templates" does not
   exist'. Adds migration 0092 to create the table (and `campaigns`)
   to match the Drizzle schema. Uses CREATE TABLE IF NOT EXISTS,
   gen_random_uuid() PKs, and the standard set_updated_at trigger
   pattern from 0001_init.sql.

2. `/admin/communications/page.tsx` resolved `effectiveBrandId`
   with a hard-coded UUID ('64294306-...') for sessions without a
   brand (e.g., dev platform_admin). That UUID isn't in the local
   dev DB (brands are '11111111-...' and '22222222-...'), so the
   modal would FK-violate on insert with 'violates foreign key
   constraint email_templates_brand_id_fkey'. Replaced with a
   `listBrandsForAdmin()` lookup that picks the first accessible
   brand.

3. `listBrandsForAdmin()` (`src/actions/brands.ts`) was SELECTing
   `logo_url` from `brands`, but that column doesn't exist (the
   brands table only has id/name/slug/plan_tier/limits/stripe_*/...).
   The query threw 'column "logo_url" does not exist', got caught
   by the silent try/catch, returned [], which made #2 above render
   the page with brandId="" — and any submit would then error with
   'invalid input syntax for type uuid: ""'. Removed logo_url
   from the SELECT; BrandListItem.logo_url is always null until a
   future migration adds the column.

E2E verified: opening /admin/communications → Templates tab → New
Template → fill name → Create Template inserts a row in
email_templates with the correct brand_id.

src/actions/brands.ts

@@ -24,20 +24,20 @@ export async function listBrandsForAdmin(): Promise<BrandListItem[]> {
   try {
     if (adminUser.role === "platform_admin") {
       const { rows } = await pool.query<BrandListItem>(
-        `SELECT id, name, slug, logo_url FROM brands ORDER BY name`,
+        `SELECT id, name, slug FROM brands ORDER BY name`,
       );
-      return rows;
+      return rows.map((r) => ({ ...r, logo_url: null }));
     }
 
     if (adminUser.brand_ids.length === 0) return [];
 
     const { rows } = await pool.query<BrandListItem>(
-      `SELECT id, name, slug, logo_url FROM brands
+      `SELECT id, name, slug FROM brands
        WHERE id = ANY($1::uuid[])
        ORDER BY name`,
       [adminUser.brand_ids],
     );
-    return rows;
+    return rows.map((r) => ({ ...r, logo_url: null }));
   } catch {
     return [];
   }