feat: auto-detect timezone/locale from proxy IP via geoip

Adds geoip=True parameter to launch(), launch_async(), and
launch_context(). Resolves proxy exit IP → MaxMind GeoLite2-City
lookup → timezone + locale. Downloads ~70MB DB on first use from
P3TERX mirror, caches in ~/.cloakbrowser/geoip/.

Optional deps: pip install cloakbrowser[geoip] / npm install mmdb-lib
Explicit timezone/locale always override auto-detected values.

js/tests/geoip.test.ts

@@ -0,0 +1,45 @@
+import { describe, it, expect } from "vitest";
+import { COUNTRY_LOCALE_MAP, resolveProxyIp } from "../src/geoip.js";
+
+describe("resolveProxyIp", () => {
+  it("returns literal IPv4 from proxy URL", async () => {
+    expect(await resolveProxyIp("http://10.50.96.5:8888")).toBe("10.50.96.5");
+  });
+
+  it("handles proxy URL with credentials", async () => {
+    expect(await resolveProxyIp("http://user:pass@10.50.96.5:8888")).toBe(
+      "10.50.96.5"
+    );
+  });
+
+  it("resolves localhost", async () => {
+    const ip = await resolveProxyIp("http://localhost:8888");
+    expect(ip).toBeTruthy();
+    expect(["127.0.0.1", "::1"]).toContain(ip);
+  });
+
+  it("returns null for invalid URL", async () => {
+    expect(await resolveProxyIp("not-a-url")).toBeNull();
+  });
+
+  it("returns null for empty string", async () => {
+    expect(await resolveProxyIp("")).toBeNull();
+  });
+});
+
+describe("COUNTRY_LOCALE_MAP", () => {
+  it("contains common countries", () => {
+    for (const code of ["US", "GB", "DE", "FR", "JP", "BR", "IL", "RU"]) {
+      expect(COUNTRY_LOCALE_MAP[code]).toBeDefined();
+    }
+  });
+
+  it("values are BCP 47 language-REGION format", () => {
+    for (const [code, locale] of Object.entries(COUNTRY_LOCALE_MAP)) {
+      const parts = locale.split("-");
+      expect(parts).toHaveLength(2);
+      expect(parts[0]).toMatch(/^[a-z]{2,3}$/);
+      expect(parts[1]).toMatch(/^[A-Z]{2}$/);
+    }
+  });
+});