Fix auth interception integer overflow

[krichprollsch]

With proxy auth interception we had a crash (with puppeteer or playwright scenarios)

DEBUG cdp : request intercept . . . . . . . . . . . . . . . . [+2411ms]
      state = continue with auth
      id = 1
      response = ProvideCredentials

thread 173974 panic: integer overflow
/home/pierre/wrk/browser/src/http/Client.zig:233:22: 0x3268ee5 in continueTransfer (lightpanda)
    self.intercepted -= 1;
                     ^
/home/pierre/wrk/browser/src/cdp/domains/fetch.zig:316:52: 0x3269eba in continueWithAuth__anon_129776 (lightpanda)
    try bc.cdp.browser.http_client.continueTransfer(transfer);
                                                   ^
/home/pierre/wrk/browser/src/cdp/domains/fetch.zig:42:53: 0x31e5012 in processMessage__anon_114148 (lightpanda)
        .continueWithAuth => return continueWithAuth(cmd),
                                                    ^
/home/pierre/wrk/browser/src/cdp/cdp.zig:206:95: 0x31e4339 in dispatchCommand__anon_114026 (lightpanda)
                    asUint(u40, "Fetch") => return @import("domains/fetch.zig").processMessage(command),
                                                                                              ^
/home/pierre/wrk/browser/src/cdp/cdp.zig:164:32: 0x31e6b37 in dispatch__anon_113835 (lightpanda)
                dispatchCommand(&command, input.method) catch |err| {
                               ^
/home/pierre/wrk/browser/src/cdp/cdp.zig:112:33: 0x31e6f87 in processMessage (lightpanda)
            return self.dispatch(arena.allocator(), self, msg);
                                ^
/home/pierre/wrk/browser/src/cdp/cdp.zig:105:32: 0x316e497 in handleMessage (lightpanda)
            self.processMessage(msg) catch return false;
                               ^
/home/pierre/wrk/browser/src/server.zig:462:56: 0x316e36d in processWebsocketMessage (lightpanda)
                .text, .binary => if (cdp.handleMessage(msg.data) == false) {
                                                       ^
/home/pierre/wrk/browser/src/server.zig:256:63: 0x3182651 in processData (lightpanda)
            .cdp => |*cdp| return self.processWebsocketMessage(cdp),
                                                              ^
/home/pierre/wrk/browser/src/server.zig:245:32: 0x318281f in readSocket (lightpanda)
        return self.processData(n) catch false;
                               ^
/home/pierre/wrk/browser/src/server.zig:153:46: 0x3182d43 in readLoop (lightpanda)
                    if (try client.readSocket() == false) {
                                             ^
/home/pierre/wrk/browser/src/server.zig:111:26: 0x31839bc in run (lightpanda)
            self.readLoop(socket, timeout_ms) catch |err| {
                         ^
/home/pierre/wrk/browser/src/main.zig:142:23: 0x31be511 in run (lightpanda)
            server.run(address, timeout) catch |err| {
                      ^
/home/pierre/wrk/browser/src/main.zig:46:8: 0x31c01e3 in main (lightpanda)
    run(alloc) catch |err| {
       ^
/usr/local/zig-0.15.1/lib/std/start.zig:627:37: 0x31c09bd in main (lightpanda)
            const result = root.main() catch |err| {
                                    ^
../sysdeps/nptl/libc_start_call_main.h:58:16: 0x72165622a1c9 in __libc_start_call_main (../sysdeps/x86/libc-start.c)
../csu/libc-start.c:360:3: 0x72165622a28a in __libc_start_main_impl (../sysdeps/x86/libc-start.c)
???:?:?: 0x294c024 in ??? (???)
???:?:?: 0x0 in ??? (???)
run
└─ run exe lightpanda failure
error: the following command terminated unexpectedly:
./.zig-cache/o/84f9c4fd4a9a28567aebbb9f2fab8dec/lightpanda serve --port 9223 --http_proxy http://127.0.0.1:3000 --log_level debug