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>

lib/extensions/sectors.ts

@@ -48,21 +48,12 @@ export function getExtensionsBySector(slug: SectorSlug): ExtensionDefinition[] {
   return getSector(slug)?.extensions ?? []
 }
 
-/** Extensions with a workspace and a quickAction href — for sidebar nav.
- *  Filters against the user's enabled extensions when provided. */
-export function getExtensionNavItems(
-  enabledExtensions?: { sector_slug: string; extension_slug: string }[]
-): { href: string; label: string; icon: string }[] {
+/** Extensions with a workspace and a quickAction href — for sidebar nav. */
+export function getExtensionNavItems(): { href: string; label: string; icon: string }[] {
   return getAllExtensions()
     .filter(e => {
       const key = `${e.sector}/${e.slug}`
-      if (!(key in WORKSPACES) || !e.quickAction?.href) return false
-      if (enabledExtensions) {
-        return enabledExtensions.some(
-          t => t.sector_slug === e.sector && t.extension_slug === e.slug
-        )
-      }
-      return true
+      return key in WORKSPACES && !!e.quickAction?.href
     })
     .sort((a, b) => (a.quickAction!.order ?? 0) - (b.quickAction!.order ?? 0))
     .map(e => ({