Phase 4.5: practice area integration in the Next.js UI

Backend commit 26d09d6 introduced a multi-tenant axis (practice_area +
appeal_subtype) that the vanilla UI picked up but the new Next.js
rewrite did not. Close the gap in the screens we already shipped so
future search/filter work in Phase 5 has the right data on screen.

- lib/practice-area.ts — new: enum + label maps + deriveSubtype(),
  mirrors mcp-server/src/legal_mcp/services/practice_area.py.
- lib/schemas/case.ts — two new z.enum fields on caseCreateSchema.
- lib/api/cases.ts — Case / CaseDetail gain practice_area and
  appeal_subtype as optional (cached pre-migration responses still
  parse cleanly).
- wizard/case-wizard.tsx — basics step gains a practice_area dropdown
  (future domains disabled with "(בקרוב)") and an appeal_subtype
  dropdown with auto-fill effect tracking a userTouchedSubtype ref,
  same behaviour as wireSubtypeAutofill() in the vanilla UI.
- cases/case-header.tsx — gold badge next to the status shows
  "ועדת ערר · רישוי ובנייה" when both fields are populated.
- cases/cases-table.tsx — new "תחום" column showing subtype label
  (dash for unknown). No filter yet — that's phase 5 when a second
  domain actually exists.

Plan: ~/.claude/plans/woolly-cooking-graham.md

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web-ui/src/lib/schemas/case.ts

@@ -10,6 +10,7 @@
  */
 
 import { z } from "zod";
+import type { PracticeArea, AppealSubtype } from "@/lib/practice-area";
 
 /* Appeal numbers follow the 1xxx / 8xxx / 9xxx convention from CLAUDE.md.
  * Two accepted formats, both hyphen-separated:
@@ -60,6 +61,17 @@ export const caseCreateSchema = z.object({
   expected_outcome: z.enum(
     expectedOutcomes.map((o) => o.value) as [string, ...string[]],
   ),
+  practice_area: z.enum([
+    "appeals_committee",
+    "national_insurance",
+    "labor_law",
+  ] as const satisfies readonly PracticeArea[]),
+  appeal_subtype: z.enum([
+    "building_permit",
+    "betterment_levy",
+    "compensation_197",
+    "unknown",
+  ] as const satisfies readonly AppealSubtype[]),
 });
 
 export type CaseCreateInput = z.infer<typeof caseCreateSchema>;