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/vaultik/blobcache.go

@@ -1,6 +1,7 @@
 package vaultik
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -8,6 +9,15 @@ import (
 	"sync"
 )
 
+// Sentinel errors for blob cache lookups.
+var (
+	errCacheKeyMissing     = errors.New("key not in cache")
+	errCacheReadBeyondBlob = errors.New("read beyond blob size")
+)
+
+// blobCacheFileMode is the permission mode for cached blob files.
+const blobCacheFileMode = 0o600
+
 // blobDiskCacheEntry tracks a cached blob on disk.
 type blobDiskCacheEntry struct {
 	key  string
@@ -61,54 +71,8 @@ func newBlobDiskCache(maxBytes int64) (*blobDiskCache, error) {
 	}, nil
 }
 
-func (c *blobDiskCache) path(key string) string {
-	return filepath.Join(c.dir, key)
-}
-
-func (c *blobDiskCache) unlink(e *blobDiskCacheEntry) {
-	if e.prev != nil {
-		e.prev.next = e.next
-	} else {
-		c.head = e.next
-	}
-
-	if e.next != nil {
-		e.next.prev = e.prev
-	} else {
-		c.tail = e.prev
-	}
-
-	e.prev = nil
-	e.next = nil
-}
-
-func (c *blobDiskCache) pushFront(e *blobDiskCacheEntry) {
-	e.prev = nil
-
-	e.next = c.head
-	if c.head != nil {
-		c.head.prev = e
-	}
-
-	c.head = e
-	if c.tail == nil {
-		c.tail = e
-	}
-}
-
-func (c *blobDiskCache) evictLRU() {
-	if c.tail == nil {
-		return
-	}
-
-	victim := c.tail
-	c.unlink(victim)
-	delete(c.items, victim.key)
-	c.curBytes -= victim.size
-	_ = os.Remove(c.path(victim.key))
-}
-
-// Put writes blob data to disk cache. Entries larger than maxBytes are silently skipped.
+// Put writes blob data to disk cache. Entries larger than maxBytes are
+// silently skipped.
 func (c *blobDiskCache) Put(key string, data []byte) error {
 	entrySize := int64(len(data))
 
@@ -127,7 +91,7 @@ func (c *blobDiskCache) Put(key string, data []byte) error {
 		delete(c.items, key)
 	}
 
-	err := os.WriteFile(c.path(key), data, 0600)
+	err := os.WriteFile(c.path(key), data, blobCacheFileMode)
 	if err != nil {
 		return fmt.Errorf("writing blob to cache: %w", err)
 	}
@@ -166,7 +130,8 @@ func (c *blobDiskCache) PutFromReader(key string, r io.Reader) (int64, error) {
 	}
 	c.mu.Unlock()
 
-	f, err := os.OpenFile(c.path(key), os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o600)
+	f, err := os.OpenFile(
+		c.path(key), os.O_CREATE|os.O_TRUNC|os.O_WRONLY, blobCacheFileMode)
 	if err != nil {
 		return 0, fmt.Errorf("creating cache file: %w", err)
 	}
@@ -255,13 +220,14 @@ func (c *blobDiskCache) ReadAt(key string, offset, length int64) ([]byte, error)
 	if !ok {
 		c.mu.Unlock()
 
-		return nil, fmt.Errorf("key %q not in cache", key)
+		return nil, fmt.Errorf("%w: %q", errCacheKeyMissing, key)
 	}
 
 	if offset+length > e.size {
 		c.mu.Unlock()
 
-		return nil, fmt.Errorf("read beyond blob size: offset=%d length=%d size=%d", offset, length, e.size)
+		return nil, fmt.Errorf("%w: offset=%d length=%d size=%d",
+			errCacheReadBeyondBlob, offset, length, e.size)
 	}
 
 	c.unlink(e)
@@ -379,3 +345,50 @@ func (c *blobDiskCache) Close() error {
 
 	return os.RemoveAll(c.dir)
 }
+
+func (c *blobDiskCache) path(key string) string {
+	return filepath.Join(c.dir, key)
+}
+
+func (c *blobDiskCache) unlink(e *blobDiskCacheEntry) {
+	if e.prev != nil {
+		e.prev.next = e.next
+	} else {
+		c.head = e.next
+	}
+
+	if e.next != nil {
+		e.next.prev = e.prev
+	} else {
+		c.tail = e.prev
+	}
+
+	e.prev = nil
+	e.next = nil
+}
+
+func (c *blobDiskCache) pushFront(e *blobDiskCacheEntry) {
+	e.prev = nil
+
+	e.next = c.head
+	if c.head != nil {
+		c.head.prev = e
+	}
+
+	c.head = e
+	if c.tail == nil {
+		c.tail = e
+	}
+}
+
+func (c *blobDiskCache) evictLRU() {
+	if c.tail == nil {
+		return
+	}
+
+	victim := c.tail
+	c.unlink(victim)
+	delete(c.items, victim.key)
+	c.curBytes -= victim.size
+	_ = os.Remove(c.path(victim.key))
+}