Fix golangci-lint v2 compliance, make all passes clean

- Fix 314 errcheck violations (blank identifier for unrecoverable errors)
- Fix errorlint violation (errors.Is for io.EOF)
- Remove unused serveL7Route test helper
- Simplify Duration.Seconds() selectors in tests
- Remove unnecessary fmt.Sprintf in test
- Migrate exclusion rules from issues.exclusions to linters.exclusions (v2 schema)
- Add gosec test exclusions (G115, G304, G402, G705)
- Disable fieldalignment govet analyzer (optimization, not correctness)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/mc-proxy/server.go

@@ -40,7 +40,7 @@ func serverCmd() *cobra.Command {
 			if err != nil {
 				return fmt.Errorf("opening database: %w", err)
 			}
-			defer store.Close()
+			defer func() { _ = store.Close() }()
 
 			if err := store.Migrate(); err != nil {
 				return fmt.Errorf("running migrations: %w", err)
@@ -93,7 +93,7 @@ func serverCmd() *cobra.Command {
 				}()
 				defer func() {
 					grpcSrv.GracefulStop()
-					os.Remove(cfg.GRPC.SocketPath())
+					_ = os.Remove(cfg.GRPC.SocketPath())
 				}()
 			}
 

cmd/mc-proxy/snapshot.go

@@ -32,7 +32,7 @@ func snapshotCmd() *cobra.Command {
 			if err != nil {
 				return fmt.Errorf("opening database: %w", err)
 			}
-			defer store.Close()
+			defer func() { _ = store.Close() }()
 
 			dataDir := filepath.Dir(cfg.Database.Path)
 

cmd/mc-proxy/status.go

@@ -33,7 +33,7 @@ func statusCmd() *cobra.Command {
 			if err != nil {
 				return fmt.Errorf("connecting to gRPC API: %w", err)
 			}
-			defer conn.Close()
+			defer func() { _ = conn.Close() }()
 
 			client := pb.NewProxyAdminServiceClient(conn)