feat(db): phase 4 group 1 — lib/ settings + notifications to Drizzle

Convert lib/settings.ts, lib/notifications/{in-app,email,capa-escalation,
effectiveness-recheck}.ts from Supabase PostgREST to Drizzle asAdmin queries.
Drop supabase arg from all call sites in app/api/ and cron routes. Rewrite
notification unit tests to mock @/lib/db/with-user instead of SupabaseClient.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/api/incidents/[id]/similar/route.ts

@@ -18,7 +18,7 @@ export async function GET(
 
   const supabase = await createClient()
 
-  const googleAiKey = await getApiKey(supabase, 'GOOGLE_AI_API_KEY')
+  const googleAiKey = await getApiKey('GOOGLE_AI_API_KEY')
 
   const { data: incident } = await supabase
     .from('incidents')