Fix lint errors and bump golangci-lint to v2/action v9

- Migrate .golangci.yml to golangci-lint v2 config format
- Bump golangci-lint-action from v6 (Node 20, deprecated) to v9 (Node 24)
- Fix errcheck: check fmt.Fscanln and fmt.Sscanf return values
- Fix ineffassign: replace unused vars with _ in test files
- Fix revive unused-parameter: rename unused cmd/args/r/c params to _
- Fix revive empty-block: invert if condition in push command
- Fix revive redefines-builtin-id: rename 'clear' to 'clearsigned'
- Fix revive blank-imports: add comment on modernc.org/sqlite import
- Fix unused: remove unused 'suite' and 'gen' fields from cache entry

server/restapi/api_test.go

@@ -136,7 +136,7 @@ func TestRegisterFirstUserIsAdmin(t *testing.T) {
 	h.token = resp.Token
 
 	// /me with token
-	code, body = h.do("GET", "/api/v1/me", h.token, nil)
+	code, _ = h.do("GET", "/api/v1/me", h.token, nil)
 	if code != 200 {
 		t.Fatalf("me status %d", code)
 	}
@@ -199,7 +199,7 @@ func TestLoginAndAuthFlow(t *testing.T) {
 	}
 
 	// create token
-	code, body = h.do("POST", "/api/v1/me/tokens", resp.Token, map[string]string{"name": "laptop"})
+	code, _ = h.do("POST", "/api/v1/me/tokens", resp.Token, map[string]string{"name": "laptop"})
 	if code != 201 {
 		t.Fatalf("create token status %d", code)
 	}
@@ -241,7 +241,7 @@ func TestUsersAdminOnly(t *testing.T) {
 		t.Fatalf("non-admin list users should be 403, got %d", code)
 	}
 	// admin can list users
-	code, body = h.do("GET", "/api/v1/users", admin.Token, nil)
+	code, _ = h.do("GET", "/api/v1/users", admin.Token, nil)
 	if code != 200 {
 		t.Fatalf("admin list users should be 200, got %d", code)
 	}

server/restapi/packages_test.go

@@ -149,7 +149,7 @@ func TestPushPullDeletePackage(t *testing.T) {
 	}
 
 	// list
-	code, body = h.do("GET", "/api/v1/repositories/pkgrepo/distributions/stable/packages", owner.Token, nil)
+	code, _ = h.do("GET", "/api/v1/repositories/pkgrepo/distributions/stable/packages", owner.Token, nil)
 	if code != 200 {
 		t.Fatalf("list packages status %d", code)
 	}

server/restapi/repos_test.go

@@ -31,7 +31,7 @@ func TestRepoCreateAndPermissions(t *testing.T) {
 	}
 
 	// bob cannot see it (private, not a member)
-	code, body = h.do("GET", "/api/v1/repositories/myrepo", bob.Token, nil)
+	code, _ = h.do("GET", "/api/v1/repositories/myrepo", bob.Token, nil)
 	if code != 403 {
 		t.Fatalf("bob should be forbidden from private repo, got %d", code)
 	}

server/restapi/server.go

@@ -28,7 +28,7 @@ func (api *API) ServerInfo(w http.ResponseWriter, r *http.Request) {
 }
 
 // ServerPubkey returns the ASCII-armored default signing key.
-func (api *API) ServerPubkey(w http.ResponseWriter, r *http.Request) {
+func (api *API) ServerPubkey(w http.ResponseWriter, _ *http.Request) {
 	if api.Signer == nil {
 		httputil.WriteError(w, http.StatusServiceUnavailable, httputil.CodeInternal, "no signing key configured")
 		return