fix sigsev on bind permissions denied (#2250?) (#2251)

Previous behaviour was bugged from somewhere between 1.11.3 and 1.12.0:

```bash
❯❯ frankenphp git:(main) 10:46 ./frankenphp php-server
2026/03/08 03:46:36.541 WARN    admin   admin endpoint disabled
2026/03/08 03:46:36.541 WARN    http.auto_https server is listening only on the HTTP port, so no automatic HTTPS will be applied to this server {"server_name": "php", "http_port": 80}
2026/03/08 03:46:36.542 INFO    tls.cache.maintenance   started background certificate maintenance      {"cache": "0x182aaec16500"}
2026/03/08 03:46:36.582 INFO    frankenphp      FrankenPHP started 🐘   {"php_version": "8.6.0-dev", "num_threads": 32, "max_threads": 32}
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0xb436bf]

goroutine 1 [running]:
github.com/caddyserver/caddy/v2.(*Context).Value(0x182aaedbe078?, {0x1e2d340?, 0x25e0c90?})
        <autogenerated>:1 +0x1f
github.com/caddyserver/caddy/v2/modules/caddyhttp.(*extraFieldsSlogHandler).Handle(_, {_, _}, {{0xc2635a2724e776c5, 0x67b02fd, 0x3ca5000}, {0x22f7b13, 0x17}, 0x0, 0x1b7943e, ...})
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/modules/caddyhttp/logging.go:308 +0x4c
log/slog.(*Logger).logAttrs(0x182aaea2bc30, {0x260a170?, 0x182aae96ad20?}, 0x0, {0x22f7b13, 0x17}, {0x0, 0x0, 0x0})
        /home/m/static-php-cli/pkgroot/x86_64-linux/go-xcaddy/src/log/slog/logger.go:276 +0x277
log/slog.(*Logger).LogAttrs(...)
        /home/m/static-php-cli/pkgroot/x86_64-linux/go-xcaddy/src/log/slog/logger.go:194
github.com/dunglas/frankenphp/caddy.(*FrankenPHPApp).Stop(0x182aae844300)
        /home/m/frankenphp/caddy/app.go:182 +0x14b
github.com/caddyserver/caddy/v2.run.func2(...)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:460
github.com/caddyserver/caddy/v2.run(0x25d1e48?, 0x1)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:471 +0x977
github.com/caddyserver/caddy/v2.unsyncedDecodeAndRun({0x182aaee76400, 0x3ad, 0x400}, 0x1)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:364 +0x17a
github.com/caddyserver/caddy/v2.changeConfig({0x22c19cb, 0x4}, {0x22c7b94, 0x7}, {0x182aaee76000, 0x3ad, 0x400}, {0x0, 0x0}, 0x1)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:248 +0x959
github.com/caddyserver/caddy/v2.Load({0x182aaee76000, 0x3ad, 0x400}, 0x1)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:137 +0x225
github.com/caddyserver/caddy/v2.Run(0x1fdb7a0?)
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/caddy.go:109 +0x3b
github.com/dunglas/frankenphp/caddy.cmdPHPServer({0x0?})
        /home/m/frankenphp/caddy/php-server.go:320 +0x27b6
github.com/dunglas/frankenphp/caddy.init.4.func1.WrapCommandFuncForCobra.1(0x182aaee53808, {0x22c1a77?, 0x4?, 0x22c1a03?})
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/cmd/cobra.go:151 +0x2f
github.com/spf13/cobra.(*Command).execute(0x182aaee53808, {0x3cc96a0, 0x0, 0x0})
        /home/m/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1015 +0xb14
github.com/spf13/cobra.(*Command).ExecuteC(0x182aae7fbb08)
        /home/m/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1148 +0x465
github.com/spf13/cobra.(*Command).Execute(...)
        /home/m/go/pkg/mod/github.com/spf13/cobra@v1.10.2/command.go:1071
github.com/caddyserver/caddy/v2/cmd.Main()
        /home/m/go/pkg/mod/github.com/caddyserver/caddy/v2@v2.11.2/cmd/main.go:72 +0x65
main.main()
        /home/m/frankenphp/caddy/frankenphp/main.go:14 +0xf
```

This restores it to exit cleanly again:

```bash
        /home/m/frankenphp/caddy/frankenphp/main.go:14 +0xf
❯❯ frankenphp git:(main)  10:46 go build 
❯❯ frankenphp git:(main) 10:58 ./frankenphp php-server
2026/03/08 03:58:01.533 WARN    admin   admin endpoint disabled
2026/03/08 03:58:01.533 WARN    http.auto_https server is listening only on the HTTP port, so no automatic HTTPS will be applied to this server {"server_name": "php", "http_port": 80}
2026/03/08 03:58:01.533 INFO    tls.cache.maintenance   started background certificate maintenance      {"cache": "0x850ebf79280"}
2026/03/08 03:58:01.556 INFO    tls.cache.maintenance   stopped background certificate maintenance      {"cache": "0x850ebf79280"}
2026/03/08 03:58:01.556 INFO    http    servers shutting down with eternal grace period
Error: loading new config: http app module: start: listening on :80: listen tcp :80: bind: permission denied
```

Author: henderkes

caddy/app.go

@@ -176,17 +176,15 @@ func (f *FrankenPHPApp) Start() error {
 }
 
 func (f *FrankenPHPApp) Stop() error {
-	ctx := caddy.ActiveContext()
-
-	if f.logger.Enabled(caddy.ActiveContext(), slog.LevelInfo) {
-		f.logger.LogAttrs(ctx, slog.LevelInfo, "FrankenPHP stopped 🐘")
+	if f.logger.Enabled(f.ctx, slog.LevelInfo) {
+		f.logger.LogAttrs(f.ctx, slog.LevelInfo, "FrankenPHP stopped 🐘")
 	}
 
 	// attempt a graceful shutdown if caddy is exiting
 	// note: Exiting() is currently marked as 'experimental'
 	// https://github.com/caddyserver/caddy/blob/e76405d55058b0a3e5ba222b44b5ef00516116aa/caddy.go#L810
 	if caddy.Exiting() {
-		frankenphp.DrainWorkers()
+		frankenphp.Shutdown()
 	}
 
 	// reset the configuration so it doesn't bleed into later tests

frankenphp.go

@@ -211,7 +211,7 @@ func calculateMaxThreads(opt *opt) (numWorkers int, _ error) {
 		return numWorkers, nil
 	}
 
-	if !maxThreadsIsSet && !numThreadsIsSet {
+	if !numThreadsIsSet {
 		if numWorkers >= maxProcs {
 			// Start at least as many threads as workers, and keep a free thread to handle requests in non-worker mode
 			opt.numThreads = numWorkers + 1