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/log/tty_handler.go

@@ -94,6 +94,11 @@ func (h *TTYHandler) Handle(_ context.Context, r slog.Record) error {
 			if a.Key == "bytes" {
 				value = formatBytes(a.Value.Int64())
 			}
+		case slog.KindAny, slog.KindBool, slog.KindFloat64, slog.KindString,
+			slog.KindTime, slog.KindUint64, slog.KindGroup, slog.KindLogValuer:
+			// Plain string form above is already correct for these kinds.
+		default:
+			// Future kinds also use the plain string form.
 		}
 
 		_, _ = fmt.Fprintf(h.out, " %s%s%s=%s%s%s",
@@ -109,26 +114,27 @@ func (h *TTYHandler) Handle(_ context.Context, r slog.Record) error {
 }
 
 // WithAttrs returns a new handler with the given attributes.
-func (h *TTYHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+func (h *TTYHandler) WithAttrs(_ []slog.Attr) slog.Handler {
 	return h // Simplified for now
 }
 
 // WithGroup returns a new handler with the given group name.
-func (h *TTYHandler) WithGroup(name string) slog.Handler {
+func (h *TTYHandler) WithGroup(_ string) slog.Handler {
 	return h // Simplified for now
 }
 
 // formatDuration formats a duration in a human-readable way
 func formatDuration(d time.Duration) string {
-	if d < time.Millisecond {
+	switch {
+	case d < time.Millisecond:
 		return fmt.Sprintf("%dµs", d.Microseconds())
-	} else if d < time.Second {
+	case d < time.Second:
 		return fmt.Sprintf("%dms", d.Milliseconds())
-	} else if d < time.Minute {
+	case d < time.Minute:
 		return fmt.Sprintf("%.1fs", d.Seconds())
+	default:
+		return d.String()
 	}
-
-	return d.String()
 }
 
 // formatBytes formats bytes in a human-readable way