style: adopt golangci-lint v2 and resolve all findings

Add .golangci.yml (v2): the standard linters plus bodyclose, errorlint, noctx, misspell, rowserrcheck, sqlclosecheck, unconvert, usestdlibvars, with gofumpt + goimports formatters. Enable the std-error-handling exclusion preset for idiomatic Close/Remove/Setenv ignores; scope-exclude SA1019 (parser.ParseDir in tools/openapigen) and ST1005 (intentional capitalized user-facing error copy that tests assert verbatim). No inline nolint directives were introduced.

Resolve all 217 findings behavior-preserving: gofumpt/goimports formatting, explicit blank assignment on intentionally ignored errors, errors.Is/errors.As and %w wrapping, context-aware stdlib calls (CommandContext/QueryContext/NewRequestWithContext/Dialer), staticcheck simplifications, removed redundant conversions, http.StatusOK and http.MethodGet, inlined the go:fix intPtr helper, and deferred sql rows Close. Add a golangci CI job mirroring the existing Go jobs.

internal/web/service/outbound/outbound.go

@@ -1,6 +1,7 @@
 package outbound
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"net"
@@ -196,7 +197,7 @@ func (s *OutboundService) testOutboundTCP(outboundJSON string) (*TestOutboundRes
 func probeTCPEndpoint(endpoint string, timeout time.Duration) TestEndpointResult {
 	r := TestEndpointResult{Address: endpoint}
 	start := time.Now()
-	conn, err := net.DialTimeout("tcp", endpoint, timeout)
+	conn, err := (&net.Dialer{Timeout: timeout}).DialContext(context.Background(), "tcp", endpoint)
 	r.Delay = time.Since(start).Milliseconds()
 	if err != nil {
 		r.Error = err.Error()