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/crypto/encryption.go

@@ -1,3 +1,5 @@
+// Package crypto provides thread-safe age encryption and decryption
+// helpers used to protect blob and metadata content.
 package crypto
 
 import (
@@ -11,6 +13,10 @@ import (
 	"go.uber.org/fx"
 )
 
+// ErrNoRecipients is returned when an encryptor is created or updated
+// without any recipient public keys.
+var ErrNoRecipients = errors.New("at least one recipient is required")
+
 // Encryptor provides thread-safe encryption using the age encryption library.
 // It supports encrypting data for multiple recipients simultaneously, allowing
 // any of the corresponding private keys to decrypt the data. This is useful
@@ -26,7 +32,7 @@ type Encryptor struct {
 // public keys are invalid or if no recipients are specified.
 func NewEncryptor(publicKeys []string) (*Encryptor, error) {
 	if len(publicKeys) == 0 {
-		return nil, errors.New("at least one recipient is required")
+		return nil, ErrNoRecipients
 	}
 
 	recipients := make([]age.Recipient, 0, len(publicKeys))
@@ -132,7 +138,7 @@ func (e *Encryptor) EncryptWriter(dst io.Writer) (io.WriteCloser, error) {
 // of the public keys are invalid or if no recipients are specified.
 func (e *Encryptor) UpdateRecipients(publicKeys []string) error {
 	if len(publicKeys) == 0 {
-		return errors.New("at least one recipient is required")
+		return ErrNoRecipients
 	}
 
 	recipients := make([]age.Recipient, 0, len(publicKeys))
@@ -213,4 +219,6 @@ func (d *Decryptor) DecryptStream(src io.Reader) (io.Reader, error) {
 }
 
 // Module exports the crypto module for fx dependency injection.
+//
+//nolint:gochecknoglobals // fx module definitions are package globals
 var Module = fx.Module("crypto")