hscontrol: replace autocert with certmagic

Adds DNS-01 for headscale's own certificate through dns.challenge.provider,
with the same propagation check as node certificates. Storage format
changes: first start gets a new account and certificate.

Updates #2527
Updates #504

go.sum

@@ -8,6 +8,8 @@ atomicgo.dev/keyboard v0.2.10 h1:v7mvUKUZLHIggxULEIuWbT+WkkyQSgdbA201EziAhHU=
 atomicgo.dev/keyboard v0.2.10/go.mod h1:ap/z5ilnhLqYq852m6kPeTq5Z6aESGWu5mzRpJlC6aI=
 atomicgo.dev/schedule v0.1.0 h1:nTthAbhZS5YZmgYbb2+DH8uQIZcTlIrd4eYr3UQxEjs=
 atomicgo.dev/schedule v0.1.0/go.mod h1:xeUa3oAkiuHYh8bKiQBRojqAMq3PXXbJujjb0hw8pEU=
+code.pfad.fr/check v1.1.0 h1:GWvjdzhSEgHvEHe2uJujDcpmZoySKuHQNrZMfzfO0bE=
+code.pfad.fr/check v1.1.0/go.mod h1:NiUH13DtYsb7xp5wll0U4SXx7KhXQVCtRgdC96IPfoM=
 dario.cat/mergo v1.0.2 h1:85+piFYR1tMbRrLcDwR18y4UKJ3aH1Tbzi24VRW1TK8=
 dario.cat/mergo v1.0.2/go.mod h1:E/hbnu0NxMFBjpMIE34DRGLWqDy0g5FuKDhCb31ngxA=
 filippo.io/edwards25519 v1.2.0 h1:crnVqOiS4jqYleHd9vaKZ+HKtHfllngJIiOpNpoJsjo=
@@ -92,6 +94,10 @@ github.com/bradfitz/monogok v0.0.0-20260630033929-b1eef977b41f h1:voy0korWbg2e1g
 github.com/bradfitz/monogok v0.0.0-20260630033929-b1eef977b41f/go.mod h1:TG1HbU9fRVDnNgXncVkKz9GdvjIvqquXjH6QZSEVmY4=
 github.com/bradfitz/reco v0.0.0-20260929154613-b883fbd17e3f h1:jdXGSp5Ge5/kzikuxGOw9+6HSStUjkNBJZjGNtpItek=
 github.com/bradfitz/reco v0.0.0-20260929154613-b883fbd17e3f/go.mod h1:oiCPXxBoDKSkb/RGEZwAZk8y/fwDlQ1vYlBbNRxPysw=
+github.com/caddyserver/certmagic v0.25.6 h1:vHMtFSLKTa6kuZz6w0SnRMpQ388tSkww8ye355BgAM4=
+github.com/caddyserver/certmagic v0.25.6/go.mod h1:xq6cRNimqW+Tv91XNc5lNHs2XYTsLhQhYiH01H4AySs=
+github.com/caddyserver/zerossl v0.1.6 h1:1yrhTx5DWi43wOJPQ+Y4mVl++EPmSqqT/4REW//lsas=
+github.com/caddyserver/zerossl v0.1.6/go.mod h1:CxA0acn7oEGO6//4rtrRjYgEoa4MFw/XofZnrYwGqG4=
 github.com/cenkalti/backoff/v4 v4.3.0 h1:MyRJ/UdXutAwSAT+s3wNd7MfTIcy71VQueUuFK343L8=
 github.com/cenkalti/backoff/v4 v4.3.0/go.mod h1:Y3VNntkOUPxTVeUxJ/G5vcM//AlwfmyYozVcomhLiZE=
 github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
@@ -361,6 +367,8 @@ github.com/mdlayher/sdnotify v1.0.0 h1:Ma9XeLVN/l0qpyx1tNeMSeTjCPH6NtuD6/N9XdTlQ
 github.com/mdlayher/sdnotify v1.0.0/go.mod h1:HQUmpM4XgYkhDLtd+Uad8ZFK1T9D5+pNxnXQjCeJlGE=
 github.com/mdlayher/socket v0.7.0 h1:qVREPVwtUMg17pwvveQxpurq0PVisMxi3FGgpsorMYQ=
 github.com/mdlayher/socket v0.7.0/go.mod h1:f7iKql2EK/rfsWYDKofKjk2Ig7I+6HQWdMIdn1tO4A4=
+github.com/mholt/acmez/v3 v3.1.7 h1:XTqpuUcRdRoIBuDoI+M4mCnRnPTPN4rqH3Mb723Rg4U=
+github.com/mholt/acmez/v3 v3.1.7/go.mod h1:Lwv6P/czh/AOq+c99tAzP68/VP92s+8y+hDs4FCgxvo=
 github.com/miekg/dns v1.1.73 h1:uhT8nJxmTrPJYClxVxTCX+CVn6qnzSiybRk72Z6DgrE=
 github.com/miekg/dns v1.1.73/go.mod h1:RW2Obtfd5NZHvOFe3zYG0W8koWOQtAzyHaLo8vASBuQ=
 github.com/mitchellh/go-ps v1.0.0 h1:i6ampVEEF4wQFF+bkYfwYgY+F/uYJDktmvLPf7qIgjc=
@@ -538,6 +546,12 @@ github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415/go.mod h1:
 github.com/xeipuuv/gojsonschema v1.2.0 h1:LhYJRs+L4fBtjZUfuSZIKGeVu0QRy8e5Xi7D17UxZ74=
 github.com/xeipuuv/gojsonschema v1.2.0/go.mod h1:anYRn/JVcOK2ZgGU+IjEV4nwlhoK5sQluxsYJ78Id3Y=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+github.com/zeebo/assert v1.1.0 h1:hU1L1vLTHsnO8x8c9KAR5GmM5QscxHg5RNU5z5qbUWY=
+github.com/zeebo/assert v1.1.0/go.mod h1:Pq9JiuJQpG8JLJdtkwrJESF0Foym2/D9XMU5ciN/wJ0=
+github.com/zeebo/blake3 v0.2.4 h1:KYQPkhpRtcqh0ssGYcKLG1JYvddkEA8QwCM/yBqhaZI=
+github.com/zeebo/blake3 v0.2.4/go.mod h1:7eeQ6d2iXWRGF6npfaxl2CU+xy2Fjo2gxeyZGCRUjcE=
+github.com/zeebo/pcg v1.0.1 h1:lyqfGeWiv4ahac6ttHs+I5hwtH/+1mrhlCtVNQM2kHo=
+github.com/zeebo/pcg v1.0.1/go.mod h1:09F0S9iiKrwn9rlI5yjLkmrug154/YRW6KnnXVDM/l4=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
 go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.70.0 h1:LMuyCAyfalSjDyjdC65nK6N0zoTT63+E/u95X0JovZI=
@@ -560,6 +574,12 @@ go.opentelemetry.io/proto/otlp v1.10.0 h1:IQRWgT5srOCYfiWnpqUYz9CVmbO8bFmKcwYxpu
 go.opentelemetry.io/proto/otlp v1.10.0/go.mod h1:/CV4QoCR/S9yaPj8utp3lvQPoqMtxXdzn7ozvvozVqk=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
+go.uber.org/multierr v1.11.0 h1:blXXJkSxSSfBVBlC76pxqeO+LN3aDfLQo+309xJstO0=
+go.uber.org/multierr v1.11.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
+go.uber.org/zap v1.28.0 h1:IZzaP1Fv73/T/pBMLk4VutPl36uNC+OSUh3JLG3FIjo=
+go.uber.org/zap v1.28.0/go.mod h1:rDLpOi171uODNm/mxFcuYWxDsqWSAVkFdX4XojSKg/Q=
+go.uber.org/zap/exp v0.3.0 h1:6JYzdifzYkGmTdRR59oYH+Ng7k49H9qVpWwNSsGJj3U=
+go.uber.org/zap/exp v0.3.0/go.mod h1:5I384qq7XGxYyByIhHm6jg5CHkGY0nsTfbDLgDDlgJQ=
 go.yaml.in/yaml/v2 v2.4.4 h1:tuyd0P+2Ont/d6e2rl3be67goVK4R6deVxCUX5vyPaQ=
 go.yaml.in/yaml/v2 v2.4.4/go.mod h1:gMZqIpDtDqOfM0uNfy0SkpRhvUryYH0Z6wdMYcacYXQ=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=