feat(assets): choose furniture bundle ext via FURNI_BUNDLE_EXT

Bundle the remaining imaging hardening and the host/CI fixes from the
"Doe alles" pass into one release.

Furniture:
- Resolve the local bundle extension from FURNI_BUNDLE_EXT (".hab" default,
  ".nitro" for a stock Nitro client). The configured extension is written by
  imports/repairs and preferred on lookup; the other stays a legacy fallback.

Imaging:
- Avatar proxy sends s-maxage=86400 + stale-while-revalidate (300/3600 for the
  fallback path) so the edge can hold a render a day.
- Cloudflare cache rule now covers /api/imaging/ (verified MISS->HIT live).
- Document that bare /imaging is shadowed by the edge proxy to the renderer.

Ops/CI:
- docker-update.sh skips a CI-managed host (exit 0) instead of failing cron.
- ci-deploy.sh runs the cross-browser imaging gate (chromium+firefox+webkit)
  against the candidate before cutover; DEPLOY_SKIP_CROSS_BROWSER=1 as escape.
- scripts/imager-health-alert.sh alerts (Discord) on imager up/down transitions;
  runs from cron every 5 minutes.

Tests:
- Furniture bundle-ext resolver + FURNI_BUNDLE_EXT wiring.
- Imaging performance budget (bytes + warm latency).
- classifyDdos: /api/imaging/* stays in the api bucket.

src/lib/furni/classname.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
 import {
 	getBaseClassname,
 	getBundleFileName,
@@ -11,6 +11,7 @@ import {
 	getSwfFileName,
 	isValidClassname,
 	normalizeClassname,
+	resolveLocalBundleExt,
 	SOURCE_BUNDLE_EXT,
 } from "./classname";
 
@@ -61,6 +62,44 @@ describe("normalizeClassname", () => {
 	});
 });
 
+describe("resolveLocalBundleExt", () => {
+	it("defaults to .hab", () => {
+		expect(resolveLocalBundleExt(undefined)).toBe(".hab");
+		expect(resolveLocalBundleExt("")).toBe(".hab");
+	});
+	it("accepts .nitro and the bare form", () => {
+		expect(resolveLocalBundleExt(".nitro")).toBe(".nitro");
+		expect(resolveLocalBundleExt("nitro")).toBe(".nitro");
+		expect(resolveLocalBundleExt("NITRO")).toBe(".nitro");
+	});
+	it("accepts .hab and the bare form", () => {
+		expect(resolveLocalBundleExt(".hab")).toBe(".hab");
+		expect(resolveLocalBundleExt("HAB")).toBe(".hab");
+	});
+	it("falls back to .hab for unknown values", () => {
+		expect(resolveLocalBundleExt("swf")).toBe(".hab");
+	});
+});
+
+describe("FURNI_BUNDLE_EXT wiring", () => {
+	afterEach(() => {
+		vi.unstubAllEnvs();
+		vi.resetModules();
+	});
+
+	it("prefers the configured extension and keeps the other as fallback", async () => {
+		vi.stubEnv("FURNI_BUNDLE_EXT", ".nitro");
+		vi.resetModules();
+		const mod = await import("./classname");
+		expect(mod.LOCAL_BUNDLE_EXT).toBe(".nitro");
+		expect(mod.getNitroFileName("sofa_blue")).toBe("sofa_blue.nitro");
+		expect(mod.getLocalBundleFileNames("sofa_blue")).toEqual([
+			"sofa_blue.nitro",
+			"sofa_blue.hab",
+		]);
+	});
+});
+
 describe("isValidClassname", () => {
 	it("accepts lowercase letters, digits and allowed symbols", () => {
 		expect(isValidClassname("chair_basic")).toBe(true);