Add image listing and asset management

Show images in asset directories with preview, rename, replacement, and trash recovery. Update local Markdown references when images move and restore original files if related metadata cannot be committed.

Refresh image previews after replacement and compare actual contents when deduplicating subsequent uploads.

internal/vault/images.go

@@ -0,0 +1,125 @@
+package vault
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"html"
+	"io"
+	"io/fs"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// ReplaceImage 原位替换已有图片，保留所有引用路径；不允许借此创建文件或改变格式。
+func (v *Vault) ReplaceImage(rel, filename string, r io.Reader, limit int64) error {
+	if !IsImage(rel) || !strings.EqualFold(path.Ext(rel), path.Ext(filename)) {
+		return fmt.Errorf("%w：请选择与原图片扩展名相同的文件", ErrInvalidPath)
+	}
+	p, err := v.abs(rel)
+	if err != nil {
+		return err
+	}
+	data, err := io.ReadAll(io.LimitReader(r, limit+1))
+	if err != nil {
+		return err
+	}
+	if int64(len(data)) > limit {
+		return ErrTooLarge
+	}
+	if len(data) == 0 {
+		return fmt.Errorf("%w：图片不能为空", ErrInvalidPath)
+	}
+	v.mu.Lock()
+	defer v.mu.Unlock()
+	info, err := os.Lstat(p)
+	if errors.Is(err, fs.ErrNotExist) {
+		return ErrNotFound
+	}
+	if err != nil {
+		return err
+	}
+	if !info.Mode().IsRegular() {
+		return ErrInvalidPath
+	}
+	return atomicWrite(p, data)
+}
+
+type imageLinkChange struct {
+	path          string
+	before, after []byte
+}
+
+// 调用方持有写锁；所有原始内容留到移动成功，以便复合操作失败时回滚。
+func (v *Vault) imageLinkChanges(from, to string) ([]imageLinkChange, error) {
+	entries, err := v.Tree()
+	if err != nil {
+		return nil, err
+	}
+	var changes []imageLinkChange
+	for _, e := range entries {
+		if e.Dir || !IsNote(e.Path) {
+			continue
+		}
+		p := filepath.Join(v.root, filepath.FromSlash(e.Path))
+		before, err := os.ReadFile(p)
+		if err != nil {
+			return nil, err
+		}
+		after, err := rewriteImageLinks(before, e.Path, from, to)
+		if err != nil {
+			return nil, err
+		}
+		if !bytes.Equal(before, after) {
+			changes = append(changes, imageLinkChange{p, before, after})
+		}
+	}
+	return changes, nil
+}
+
+func rewriteImageLinks(content []byte, note, from, to string) ([]byte, error) {
+	rel, err := filepath.Rel(filepath.FromSlash(path.Dir(note)), filepath.FromSlash(to))
+	if err != nil {
+		return nil, err
+	}
+	transform := func(text []byte) []byte {
+		spans := importLinkSpans(text)
+		sort.Slice(spans, func(i, j int) bool { return spans[i].start < spans[j].start })
+		var out []byte
+		last := 0
+		for _, span := range spans {
+			if span.start < last {
+				continue
+			}
+			target := string(text[span.start:span.end])
+			if span.html {
+				target = html.UnescapeString(target)
+			} else {
+				target = markdownEscape.ReplaceAllString(target, "$1")
+			}
+			u, err := url.Parse(target)
+			if err != nil || u.IsAbs() || u.Host != "" || strings.HasPrefix(target, "/") || u.Path == "" || path.Clean(path.Join(path.Dir(note), u.Path)) != from {
+				continue
+			}
+			replacement := EscapeLinkPath(filepath.ToSlash(rel))
+			if u.RawQuery != "" {
+				replacement += "?" + u.RawQuery
+			}
+			if u.Fragment != "" {
+				replacement += "#" + u.EscapedFragment()
+			}
+			if span.html {
+				replacement = html.EscapeString(replacement)
+			}
+			out = append(out, text[last:span.start]...)
+			out = append(out, replacement...)
+			last = span.end
+		}
+		return append(out, text[last:]...)
+	}
+	return transformMarkdownLines(content, importRef, func(line []byte) []byte { return transformOutsideCode(line, transform) }), nil
+}