feat: AI API Setting page with 4 provider sections and toggles

Add OpenAI, Claude AI, and DentalManagement AI sections to the AI API
Setting page, each with a masked API key input and an on/off toggle
(defaulting to off). Rename sidebar label from "Google AI Settings" to
"AI API Setting". Add provider-key and provider-enabled backend endpoints
and extend the AiSettings schema with 6 new fields.

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

packages/db/generated/prisma/schema.prisma

@@ -600,6 +600,13 @@ model AiSettings {
   id                Int     @id @default(autoincrement())
   userId            Int     @unique
   apiKey            String
+  aiEnabled         Boolean @default(true)
+  openAiKey         String  @default("")
+  openAiEnabled     Boolean @default(true)
+  claudeAiKey       String  @default("")
+  claudeAiEnabled   Boolean @default(true)
+  dentalMgmtKey     String  @default("")
+  dentalMgmtEnabled Boolean @default(true)
   afterHoursEnabled Boolean @default(true)
   openPhoneReply    Boolean @default(false)