feat: add Procedure Duration/Time Slot settings and custom appointment type

- Add Settings > Advanced > Procedure Duration/Time Slot page with three sections:
  1. Procedure Duration: CDT codes with durations (editable table, save per section)
  2. Doctor Time Slot: drag-to-block visual grid (A/B/C columns, 8 AM–9 PM, edit/delete slots)
  3. Hygienist Time Slot: procedure descriptions with durations
- Backend: ProcedureTimeslot Prisma model, storage, and GET/PUT /api/procedure-timeslot route
- DB migration: procedure_timeslot table
- Appointment form: when type is "Other", show a free-text input for custom description; saved as other:<description> and decoded for display on the schedule card

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

packages/db/prisma/migrations/20260505000000_add_procedure_timeslot/migration.sql

@@ -0,0 +1,10 @@
+CREATE TABLE "procedure_timeslot" (
+    "id" SERIAL NOT NULL,
+    "userId" INTEGER NOT NULL,
+    "data" JSONB NOT NULL,
+    CONSTRAINT "procedure_timeslot_pkey" PRIMARY KEY ("id")
+);
+
+ALTER TABLE "procedure_timeslot" ADD CONSTRAINT "procedure_timeslot_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+CREATE UNIQUE INDEX "procedure_timeslot_userId_key" ON "procedure_timeslot"("userId");