Update golangci-lint to v2.12.2 with canonical config

Bump golangci-lint from v2.10.1 to v2.12.2 in the Dockerfile lint
stage (tag+digest pin) and script/bootstrap release-archive pins
(linux amd64/arm64 sha256s). Replace .golangci.yml with the canonical
v2-layout config so linter settings (lll 88, funlen 80/50, cyclop 15,
dupl 100) actually apply.

Fix all findings surfaced by the new linter and config:

- noctx: use httptest.NewRequestWithContext in all tests
- gosec G710/G703: route app redirects through a path-escaping
  redirectToApp helper; annotate internal log path usage
- goconst: introduce shared constants for template/JSON keys and
  repeated test literals
- lll: wrap lines to the 88-column limit
- dupl: extract shared helpers (generic findAllByAppID in models,
  deleteAppResource in handlers, parsePush in webhook payloads,
  table-driven/helper-based test dedup)
- nolintlint: drop nolint directives made obsolete by the new limits

Record the change in TODO.md; make check is green.

internal/handlers/sanitize.go

@@ -5,8 +5,11 @@ import (
 	"strings"
 )
 
-// ansiEscapePattern matches ANSI escape sequences (CSI, OSC, and single-character escapes).
-var ansiEscapePattern = regexp.MustCompile(`(\x1b\[[0-9;]*[a-zA-Z]|\x1b\][^\x07]*\x07|\x1b[^[\]])`)
+// ansiEscapePattern matches ANSI escape sequences (CSI, OSC, and
+// single-character escapes).
+var ansiEscapePattern = regexp.MustCompile(
+	`(\x1b\[[0-9;]*[a-zA-Z]|\x1b\][^\x07]*\x07|\x1b[^[\]])`,
+)
 
 // SanitizeLogs strips ANSI escape sequences and non-printable control characters
 // from container log output. Newlines (\n), carriage returns (\r), and tabs (\t)