refactor: remove extension toggle system — compiled-in extensions are always active (#59)

The runtime toggle system (extension_toggles table, API routes, hooks, UI components)
added unnecessary complexity. Extensions controlled via extensions.config.json at build
time are now always active for all users. This removes ~835 lines of toggle-related code
including API routes, DB queries, the ExtensionToggleButton component, useEnabledExtensions
and useExtensionToggle hooks, and the toggle-check module. AI consent gating remains
unchanged.

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

tests/helpers.ts

@@ -17,7 +17,6 @@ import type {
   CompanySettings,
   InvoiceInboxItem,
 } from '@/types'
-import type { ExtensionToggle } from '@/lib/extensions/types'
 
 // ============================================================
 // Chainable Supabase mock
@@ -487,21 +486,6 @@ export function makeInvoiceInboxItem(
   }
 }
 
-export function makeExtensionToggle(
-  overrides: Partial<ExtensionToggle> = {}
-): ExtensionToggle {
-  return {
-    id: nextId(),
-    user_id: 'user-1',
-    sector_slug: 'general',
-    extension_slug: 'receipt-ocr',
-    enabled: true,
-    created_at: '2024-01-01T00:00:00Z',
-    updated_at: '2024-01-01T00:00:00Z',
-    ...overrides,
-  }
-}
-
 // ============================================================
 // API Route Test Helpers
 // ============================================================