feat(security): Cloudflare-aware IP trust and admin-tunable anti-DDoS

- resolveClientIp: trust cf-connecting-ip only behind cf-ray/cdn-loop, use nginx x-real-ip otherwise (anti-spoof)
- antiddos-config: Redis-backed live config (antiddos:config) with 30s cache, 13 ANTI_DDOS_* env vars
- ddos-guard: consume tunable rates/tiers via getAntiddosConfig
- admin panel at /admin/devops/antiddos (save/reset/unban actions, PERMS.SETTINGS_VIEW)
- register new admin page in housekeeping migration matrix (146 -> 147)

src/features/housekeeping/migration/system.ts

@@ -272,6 +272,36 @@ export const systemMigrationEntries: readonly MigrationEntry[] = [
 		localization: "PARTIAL",
 		accessibility: "PARTIAL",
 	}),
+	plannedSystemEntry({
+		surface: "admin",
+		legacyPath: "/admin/devops/antiddos",
+		sourceFile: "src/app/admin/devops/antiddos/page.tsx",
+		targetPath: "/admin/system/configuration/antiddos",
+		decision: "REHOST",
+		capabilities: {
+			read: [PERMS.SETTINGS_VIEW],
+			mutate: [PERMS.SETTINGS_EDIT],
+		},
+		dependencies: {
+			queries: [
+				"antiddos:config override",
+				"WebsiteSetting antiddos_*",
+				"blocked anti-DDoS IPs",
+				"GET /api/health",
+			],
+			mutations: [
+				"saveAntiddosSettings",
+				"resetAntiddosSettings",
+				"unbanAntiddosIp",
+			],
+		},
+		auditRequirement: "MUTATION",
+		localization: "PARTIAL",
+		accessibility: "PARTIAL",
+		notes: [
+			"Tunable anti-DDoS rates and block tiers; Cloudflare detection is read-only and driven by cf-ray/cdn-loop presence",
+		],
+	}),
 	plannedSystemEntry({
 		surface: "admin",
 		legacyPath: "/admin/emulator",