feat: persist AI conversation state in DB and fix LangGraph flow bugs

- Replace in-memory Maps in aiHandoffStore with DB-backed async functions
  using new patient_conversation table (stage + aiHandoff per patient)
- Add afterHoursEnabled to ai_settings table (persists across restarts)
- Fix runtime crash in reschedule-graph: mon/tue/wed variables were out
  of scope in the next-week fallback branch (ReferenceError)
- Wire rescheduleGreeting and generalFallback chat templates through to
  LangGraph nodes so user-configured messages take effect
- Add otherNode to reminder-graph to handle unclassified patient replies
  (e.g. "I want another appointment") and route to booking flow
- Fetch chatTemplates once per webhook request instead of per stage

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

packages/db/shared/schemas/objects/AiSettingsWhereInput.schema.ts

@@ -2,6 +2,7 @@ import * as z from 'zod';
 import type { Prisma } from '../../../generated/prisma';
 import { IntFilterObjectSchema as IntFilterObjectSchema } from './IntFilter.schema';
 import { StringFilterObjectSchema as StringFilterObjectSchema } from './StringFilter.schema';
+import { BoolFilterObjectSchema as BoolFilterObjectSchema } from './BoolFilter.schema';
 import { UserScalarRelationFilterObjectSchema as UserScalarRelationFilterObjectSchema } from './UserScalarRelationFilter.schema';
 import { UserWhereInputObjectSchema as UserWhereInputObjectSchema } from './UserWhereInput.schema'
 
@@ -12,6 +13,7 @@ const aisettingswhereinputSchema = z.object({
   id: z.union([z.lazy(() => IntFilterObjectSchema), z.number().int()]).optional(),
   userId: z.union([z.lazy(() => IntFilterObjectSchema), z.number().int()]).optional(),
   apiKey: z.union([z.lazy(() => StringFilterObjectSchema), z.string()]).optional(),
+  afterHoursEnabled: z.union([z.lazy(() => BoolFilterObjectSchema), z.boolean()]).optional(),
   user: z.union([z.lazy(() => UserScalarRelationFilterObjectSchema), z.lazy(() => UserWhereInputObjectSchema)]).optional()
 }).strict();
 export const AiSettingsWhereInputObjectSchema: z.ZodType<Prisma.AiSettingsWhereInput> = aisettingswhereinputSchema as unknown as z.ZodType<Prisma.AiSettingsWhereInput>;