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/snapshot/snapshot_test.go

@@ -1,3 +1,4 @@
+//nolint:testpackage // exercises unexported SnapshotManager internals
 package snapshot
 
 import (
@@ -37,9 +38,65 @@ func copyFile(fs afero.Fs, src, dst string) error {
 	return err
 }
 
+// verifyCleanedDB opens the cleaned database and checks that the kept
+// snapshot survived while the orphan file and chunk were removed.
+func verifyCleanedDB(
+	ctx context.Context,
+	t *testing.T,
+	tempDBPath, snapshotID string,
+	file *database.File,
+	chunk *database.Chunk,
+) {
+	t.Helper()
+
+	cleanedDB, err := database.New(ctx, tempDBPath)
+	if err != nil {
+		t.Fatalf("failed to open cleaned database: %v", err)
+	}
+	defer func() {
+		err := cleanedDB.Close()
+		if err != nil {
+			t.Errorf("failed to close database: %v", err)
+		}
+	}()
+
+	cleanedRepos := database.NewRepositories(cleanedDB)
+
+	// Verify snapshot exists
+	verifySnapshot, err := cleanedRepos.Snapshots.GetByID(ctx, snapshotID)
+	if err != nil {
+		t.Fatalf("failed to get snapshot: %v", err)
+	}
+
+	if verifySnapshot == nil {
+		t.Error("snapshot should exist")
+	}
+
+	// Verify orphan file is gone
+	f, err := cleanedRepos.Files.GetByPath(ctx, file.Path.String())
+	if err != nil {
+		t.Fatalf("failed to check file: %v", err)
+	}
+
+	if f != nil {
+		t.Error("orphan file should not exist")
+	}
+
+	// Verify orphan chunk is gone
+	c, err := cleanedRepos.Chunks.GetByHash(ctx, chunk.ChunkHash.String())
+	if err != nil {
+		t.Fatalf("failed to check chunk: %v", err)
+	}
+
+	if c != nil {
+		t.Error("orphan chunk should not exist")
+	}
+}
+
 func TestCleanSnapshotDBEmptySnapshot(t *testing.T) {
 	// Initialize logger
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	fs := afero.NewOsFs()
@@ -115,53 +172,13 @@ func TestCleanSnapshotDBEmptySnapshot(t *testing.T) {
 	}
 
 	// Verify the cleaned database
-	cleanedDB, err := database.New(ctx, tempDBPath)
-	if err != nil {
-		t.Fatalf("failed to open cleaned database: %v", err)
-	}
-	defer func() {
-		err := cleanedDB.Close()
-		if err != nil {
-			t.Errorf("failed to close database: %v", err)
-		}
-	}()
-
-	cleanedRepos := database.NewRepositories(cleanedDB)
-
-	// Verify snapshot exists
-	verifySnapshot, err := cleanedRepos.Snapshots.GetByID(ctx, snapshot.ID.String())
-	if err != nil {
-		t.Fatalf("failed to get snapshot: %v", err)
-	}
-
-	if verifySnapshot == nil {
-		t.Error("snapshot should exist")
-	}
-
-	// Verify orphan file is gone
-	f, err := cleanedRepos.Files.GetByPath(ctx, file.Path.String())
-	if err != nil {
-		t.Fatalf("failed to check file: %v", err)
-	}
-
-	if f != nil {
-		t.Error("orphan file should not exist")
-	}
-
-	// Verify orphan chunk is gone
-	c, err := cleanedRepos.Chunks.GetByHash(ctx, chunk.ChunkHash.String())
-	if err != nil {
-		t.Fatalf("failed to check chunk: %v", err)
-	}
-
-	if c != nil {
-		t.Error("orphan chunk should not exist")
-	}
+	verifyCleanedDB(ctx, t, tempDBPath, snapshot.ID.String(), file, chunk)
 }
 
 func TestCleanSnapshotDBNonExistentSnapshot(t *testing.T) {
 	// Initialize logger
 	log.Initialize(log.Config{})
+	t.Parallel()
 
 	ctx := context.Background()
 	fs := afero.NewOsFs()