feat: AI-added records save with placeholders + "Added by AI" provenance

Stop blocking AI imports/proposals on missing non-critical fields. Records
the chat agent drafts now save with safe placeholders, auto-generated file
numbers, and a source="ai" marker that surfaces an "Added by AI" badge so a
clinician can review/edit them later.

Backend:
- add `source` (manual|ai) column to patients/appointments/prescriptions
  (migration 0014) + canonical types, services, validation schemas
- relax patient/appointment validation: empty file number allowed, demographic
  + type/provider/initials fall back to placeholders (initials derived from name)
- patients.generateFileNumber() auto-assigns an MRN when one is missing
- proposeAppointment accepts a name when no file number resolves; AI commits +
  /api/ai/import stamp source="ai"

Frontend:
- `source` on Appointment/Patient/Prescription types; AI commits send source="ai"
- reusable <AiBadge> shown on the Patients table/detail and prescriptions list

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/types/appointment.ts

@@ -17,6 +17,7 @@ export type Appointment = {
   type: string;
   provider: string;
   status: AppointmentStatus;
+  source: "manual" | "ai";
   createdAt: string;
   updatedAt: string;
 };

backend/src/types/patient.ts

@@ -70,4 +70,5 @@ export type Patient = {
   labs: Lab[];
   labTrend: Trend; // headline lab plotted as a sparkline
   encounters: Encounter[];
+  source?: "manual" | "ai"; // "ai" = imported/drafted by the chat agent
 };

backend/src/types/prescription.ts

@@ -16,6 +16,7 @@ export type Prescription = {
   status: PrescriptionStatus;
   duration: string | null;
   notes: string | null;
+  source: "manual" | "ai";
   createdAt: string;
   updatedAt: string;
 };