Add soft-delete (archive) for companies, admin-only

- Added deletedAt column to companies table for soft delete
- System admins see a trash icon on each company card with confirmation modal
- Archived companies are filtered from sidebar, dashboard, company list, and direct access
- Audit log entry created on archive

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/server/db/schema.ts

@@ -59,6 +59,7 @@ export const companies = pgTable('companies', {
 	description: text('description'),
 	totalBudget: numeric('total_budget', { precision: 15, scale: 2 }).notNull().default('0'),
 	currency: text('currency').notNull().default('THB'),
+	deletedAt: timestamp('deleted_at', { withTimezone: true }),
 	createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
 	updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow()
 });