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/s3/client.go

@@ -1,3 +1,5 @@
+// Package s3 wraps the AWS S3 SDK with a simplified client for vaultik's
+// bucket-and-prefix scoped object operations.
 package s3
 
 import (
@@ -42,7 +44,7 @@ type Config struct {
 // Used to suppress SDK warnings about checksums.
 type nopLogger struct{}
 
-func (nopLogger) Logf(classification logging.Classification, format string, v ...any) {}
+func (nopLogger) Logf(_ logging.Classification, _ string, _ ...any) {}
 
 // NewClient creates a new S3 client with the provided configuration.
 // It establishes a connection to the S3-compatible storage service and
@@ -105,13 +107,18 @@ type ProgressCallback func(bytesUploaded int64) error
 // The size parameter must be the exact size of the data to upload.
 // The progress callback is called periodically with the number of bytes uploaded.
 // Returns an error if the upload fails.
-func (c *Client) PutObjectWithProgress(ctx context.Context, key string, data io.Reader, size int64, progress ProgressCallback) error {
+func (c *Client) PutObjectWithProgress(
+	ctx context.Context, key string, data io.Reader,
+	size int64, progress ProgressCallback,
+) error {
 	fullKey := c.prefix + key
 
+	// uploadPartSize is 10MB for better progress granularity.
+	const uploadPartSize = 10 * 1024 * 1024
+
 	// Create an uploader with the S3 client
 	uploader := manager.NewUploader(c.s3Client, func(u *manager.Uploader) {
-		// Set part size to 10MB for better progress granularity
-		u.PartSize = 10 * 1024 * 1024
+		u.PartSize = uploadPartSize
 	})
 
 	// Create a progress reader that tracks upload progress
@@ -241,7 +248,9 @@ type ObjectInfo struct {
 // listing is complete or an error occurs. If an error occurs, it will be
 // sent as the last item with the Err field set. The recursive parameter
 // is currently unused but reserved for future use.
-func (c *Client) ListObjectsStream(ctx context.Context, prefix string, recursive bool) <-chan ObjectInfo {
+func (c *Client) ListObjectsStream(
+	ctx context.Context, prefix string, _ bool,
+) <-chan ObjectInfo {
 	ch := make(chan ObjectInfo)
 
 	go func() {