feat(ui): streamline workspace settings and remove sharing

Unify compact workspace controls and panel transitions, move directory actions into the context menu, and remove backlink UI.

Reorganize settings with searchable sections, per-setting resets, shortcut search, and accurate save feedback.

Remove sharing UI, APIs, authentication helpers, and storage code; provide a transactional cleanup script with retirement tests. Reject directories during orphan image cleanup and cover mixed-batch preservation.

internal/vault/cleanup.go

@@ -1,9 +1,6 @@
 package vault
 
-import (
-	"fmt"
-	"strings"
-)
+import "fmt"
 
 type CleanupResult struct {
 	Deleted []TrashItem   `json:"deleted"`
@@ -15,8 +12,7 @@ type CleanupSkip struct {
 }
 
 // CleanupImages 在写锁内重新扫描引用；派生索引不作为删除依据。
-// protected 返回当前有效分享的主体路径，由业务数据拥有者在检查时读取。
-func (v *Vault) CleanupImages(paths []string, protected func() ([]string, error)) (CleanupResult, error) {
+func (v *Vault) CleanupImages(paths []string) (CleanupResult, error) {
 	result := CleanupResult{Deleted: []TrashItem{}, Skipped: []CleanupSkip{}}
 	v.mu.Lock()
 	defer v.mu.Unlock()
@@ -41,10 +37,6 @@ func (v *Vault) CleanupImages(paths []string, protected func() ([]string, error)
 			references[ref.Target] = true
 		}
 	}
-	scopes, err := protected()
-	if err != nil {
-		return result, err
-	}
 	seen := map[string]bool{}
 	for _, p := range paths {
 		if seen[p] {
@@ -58,11 +50,11 @@ func (v *Vault) CleanupImages(paths []string, protected func() ([]string, error)
 		case references[p]:
 			reason = "仍被笔记引用"
 		default:
-			for _, scope := range scopes {
-				if p == scope || strings.HasPrefix(p, scope+"/") || IsNote(scope) && strings.HasPrefix(p, AssetsDir(scope)+"/") {
-					reason = "仍在有效分享范围内"
-					break
-				}
+			info, err := v.Stat(p)
+			if err != nil {
+				reason = err.Error()
+			} else if !info.Mode().IsRegular() {
+				reason = "不是图片文件"
 			}
 		}
 		if reason != "" {