Update golangci-lint to v2.12.2 with canonical config (#62)

Updates golangci-lint to v2.12.2 everywhere it is pinned and installs the canonical `.golangci.yml`, then remediates every finding the new linter/config surfaces so `make check` is green.

## Version bump

- `Dockerfile` lint stage: `golangci/golangci-lint:v2.11.3-alpine` -> `v2.12.2-alpine` (digest-pinned, date comment updated)
- `Makefile` `deps` target: `go install` moved from the old v1 module path at `@latest` to the pinned `github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.12.2`
- `.golangci.yml` replaced with the canonical config (v2 schema; settings under `linters.settings` so the thresholds actually apply; `default: all` with the standard six disables)
- `script/bootstrap` installs golangci-lint via the system package manager and carries no version pin, so it is unchanged
- CI (`.gitea/workflows/check.yml`) only runs `script/cibuild`, so it needed no change

## Lint remediation

The canonical config surfaced ~3,300 findings across 56k lines. All are fixed, behavior-preserving; incorporates and supersedes the per-package mechanical passes already merged to `main` (refs #61). Highlights:

- `err113`: dynamic errors replaced with package sentinels + `%w` wrapping; comparisons via `errors.Is`
- `goprintffuncname`: printf-style helpers renamed with an `f` suffix (`ui.Writer` message methods, `cli.ReportErrorf`, `database.Fatalf`) and all call sites updated
- `revive` stutter renames: `blob.Handler`, `blob.WithReader`, `blob.ChunkPosition`, `storage.URL`, `storage.Info`; missing doc comments added
- `contextcheck`/`noctx`: `context.Context` threaded through `blob.Packer` and the scanner call sites; context-aware `exec`/`sql` variants
- `funlen`/`cyclop`/`gocognit`/`dupl`: oversized and duplicated functions split into focused helpers (production and test code)
- tests: `t.Parallel()` added where safe (global logger init kept in the serial phase for `-race`), `t.TempDir()`/`t.Helper()` adopted, several suites converted to external test packages
- `gosec`: bounded integer conversions, `ReadHeaderTimeout` on the test HTTP server; remaining warnings suppressed per-site with justifications
- remaining `nolint` directives are rare, targeted, and each carries a reason (e.g. `nilnil` not-found contract in the repository layer, fx module globals, on-disk snake_case struct tags)
- removed the deprecated `log.LogOptions` alias (callers migrated to `log.Options`)

`make check` (tests with `-race`, lint, fmt-check) passes.

Co-authored-by: sneak <sneak@sneak.berlin>
Reviewed-on: #62
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/storage/url.go

@@ -7,8 +7,26 @@ import (
 	"strings"
 )
 
-// StorageURL represents a parsed storage URL.
-type StorageURL struct {
+// Storage URL scheme names.
+const (
+	schemeFile   = "file"
+	schemeS3     = "s3"
+	schemeRclone = "rclone"
+)
+
+// Sentinel errors for storage URL parsing.
+var (
+	ErrEmptyStorageURL   = errors.New("storage URL is empty")
+	ErrEmptyFilePath     = errors.New("file URL path is empty")
+	ErrMissingBucket     = errors.New("s3 URL missing bucket name")
+	ErrMissingRemote     = errors.New("rclone URL missing remote name")
+	ErrUnsupportedScheme = errors.New(
+		"unsupported URL scheme: must start with s3://, file://, or rclone://")
+	ErrUnsupportedStorage = errors.New("unsupported storage scheme")
+)
+
+// URL represents a parsed storage URL.
+type URL struct {
 	Scheme       string // "s3", "file", or "rclone"
 	Bucket       string // S3 bucket name (empty for file/rclone)
 	Prefix       string // Path within bucket or filesystem base path
@@ -23,20 +41,20 @@ type StorageURL struct {
 //   - s3://bucket/prefix?endpoint=host&region=us-east-1&ssl=true
 //   - file:///absolute/path/to/backup
 //   - rclone://remote/path/to/backups
-func ParseStorageURL(rawURL string) (*StorageURL, error) {
+func ParseStorageURL(rawURL string) (*URL, error) {
 	if rawURL == "" {
-		return nil, errors.New("storage URL is empty")
+		return nil, ErrEmptyStorageURL
 	}
 
 	// Handle file:// URLs
 	if after, ok := strings.CutPrefix(rawURL, "file://"); ok {
 		path := after
 		if path == "" {
-			return nil, errors.New("file URL path is empty")
+			return nil, ErrEmptyFilePath
 		}
 
-		return &StorageURL{
-			Scheme: "file",
+		return &URL{
+			Scheme: schemeFile,
 			Prefix: path,
 		}, nil
 	}
@@ -50,7 +68,7 @@ func ParseStorageURL(rawURL string) (*StorageURL, error) {
 
 		bucket := u.Host
 		if bucket == "" {
-			return nil, errors.New("s3 URL missing bucket name")
+			return nil, ErrMissingBucket
 		}
 
 		prefix := strings.TrimPrefix(u.Path, "/")
@@ -62,8 +80,8 @@ func ParseStorageURL(rawURL string) (*StorageURL, error) {
 			useSSL = false
 		}
 
-		return &StorageURL{
-			Scheme:   "s3",
+		return &URL{
+			Scheme:   schemeS3,
 			Bucket:   bucket,
 			Prefix:   prefix,
 			Endpoint: query.Get("endpoint"),
@@ -81,27 +99,27 @@ func ParseStorageURL(rawURL string) (*StorageURL, error) {
 
 		remote := u.Host
 		if remote == "" {
-			return nil, errors.New("rclone URL missing remote name")
+			return nil, ErrMissingRemote
 		}
 
 		path := strings.TrimPrefix(u.Path, "/")
 
-		return &StorageURL{
-			Scheme:       "rclone",
+		return &URL{
+			Scheme:       schemeRclone,
 			Prefix:       path,
 			RcloneRemote: remote,
 		}, nil
 	}
 
-	return nil, errors.New("unsupported URL scheme: must start with s3://, file://, or rclone://")
+	return nil, ErrUnsupportedScheme
 }
 
 // String returns a human-readable representation of the storage URL.
-func (u *StorageURL) String() string {
+func (u *URL) String() string {
 	switch u.Scheme {
-	case "file":
+	case schemeFile:
 		return "file://" + u.Prefix
-	case "s3":
+	case schemeS3:
 		endpoint := u.Endpoint
 		if endpoint == "" {
 			endpoint = "s3.amazonaws.com"
@@ -112,7 +130,7 @@ func (u *StorageURL) String() string {
 		}
 
 		return fmt.Sprintf("s3://%s (endpoint: %s)", u.Bucket, endpoint)
-	case "rclone":
+	case schemeRclone:
 		if u.Prefix != "" {
 			return fmt.Sprintf("rclone://%s/%s", u.RcloneRemote, u.Prefix)
 		}