next -> main (1.0.0 milestone) (#105)

Accumulating milestone branch. One squashed commit per closed issue; `next` is kept green and mergeable to `main` at any time without notice.

Landed so far:

- `chore: update golangci-lint to v2.12.2 with canonical config` (#54) — canonical v2-schema `.golangci.yml`, pins bumped in `Dockerfile` and `script/bootstrap`, tree at `0 issues.`. Three behaviour deltas are recorded in that PR's body: `Cache.StoreVariant` takes a context, `MetadataStorage.Store` no longer leaks temp files on failure, and the `signing_key` too-short error text gained a `value too short:` prefix.

Sequencing for the milestone is tracked in #103.

Reviewed-on: #105
Co-authored-by: clawbot <clawbot@noreply.example.org>

internal/server/http.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"time"
@@ -26,8 +27,11 @@ func (s *Server) serveUntilShutdown() {
 	s.SetupRoutes()
 
 	s.log.Info("http begin listen", "listenaddr", listenAddr)
-	if err := s.httpServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+
+	err := s.httpServer.ListenAndServe()
+	if err != nil && !errors.Is(err, http.ErrServerClosed) {
 		s.log.Error("listen error", "error", err)
+
 		if s.cancelFunc != nil {
 			s.cancelFunc()
 		}