feat: relocate import tools into studio and harden catalog/furnidata integrity

- Move /admin/import/* tools under /admin/studio/* and add studio nav, layout and tabs
- Add shared catalog maintenance panel plus a /admin/studio/maintenance tab
- Make furnidata reconciliation overwrite conflicting entries with the
  DB-authoritative items_base classname/id (surfaced via fixedConflicts)
- Add furnidata_translate_enabled setting to skip the heavy localized
  furnidata build during import (manual build-languages still forces it)
- Update staff smoke contract test for the studio hub

src/lib/staff-smoke-contract.test.ts

@@ -243,11 +243,11 @@ describe("staff smoke contract", () => {
 		);
 	});
 
-	it("ships import hub with synced badge import path", () => {
+	it("ships studio hub with synced badge import path", () => {
 		const nav = readFileSync("src/lib/admin-nav.ts", "utf8");
-		expect(nav).toContain('id: "import"');
-		expect(nav).toContain("importSubtitle");
-		expect(nav).toContain("/admin/import");
+		expect(nav).toContain('href: "/admin/studio"');
+		expect(nav).toContain('labelKey: "studio"');
+		expect(nav).toContain('"/admin/studio"');
 		expect(existsSync("src/lib/services/import-badge.ts")).toBe(true);
 		const badgeService = readFileSync(
 			"src/lib/services/import-badge.ts",