chore: update Go dependencies

[dunglas]

Run go get -u all and go mod tidy in the root and caddy/ modules.

Notable bumps:

• github.com/dunglas/mercure and mercure/caddy 1.0.3 to 1.1.1
• github.com/prometheus/client_golang 1.24.1 to 1.25.0
• github.com/shopspring/decimal 1.4.0 to 1.5.0
• golang.org/x/net 0.59.0 to 0.61.0
• golang.org/x/crypto 0.57.0 to 0.58.0