fix(local-tool): locateServerBinary 找 {app}\bin\ 子目錄（Windows/Linux installer 佈局）

根因：Windows installer 把 visiona-local-server.exe 裝到 {app}\bin\
      （.iss 的 DestDir: "{app}\bin"），但 locateServerBinary 只搜
      exeDir\visiona-local-server.exe 和 macOS bundle 專屬路徑，
      Windows/Linux 打包後的 bin/ 子目錄完全沒被搜尋，導致執行時
      "server binary not found" 嚴重錯誤。

修法：
- locateServerBinary 第一優先搜 exeDir\bin\visiona-local-server
  （Inno Setup installer / AppImage 的標準佈局）
- 開發模式 fallback 新增 payload/<goos>/bin/ 候選路徑
- 同時修正 locateBundleBinDir / locateBundledPythonAssets 的開發模式
  fallback 寫死 "payload/darwin"，改用 runtime.GOOS 動態選 payload 子目錄

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

local-tool/visiona-local/app.go

@@ -698,12 +698,13 @@ func locateBundledPythonAssets() (tarball, wheelsDir string, err error) {
 		}
 	}
 
-	// 2. 開發模式 fallback
+	// 2. 開發模式 fallback（依 GOOS 挑對應 payload 子目錄）
 	if cwd, e := os.Getwd(); e == nil {
+		osName := runtime.GOOS // darwin / windows / linux
 		candidates := []struct{ t, w string }{
-			{filepath.Join(cwd, "payload", "darwin", "python", "python.tar.gz"), filepath.Join(cwd, "payload", "darwin", "wheels")},
+			{filepath.Join(cwd, "payload", osName, "python", "python.tar.gz"), filepath.Join(cwd, "payload", osName, "wheels")},
-			{filepath.Join(cwd, "..", "payload", "darwin", "python", "python.tar.gz"), filepath.Join(cwd, "..", "payload", "darwin", "wheels")},
+			{filepath.Join(cwd, "..", "payload", osName, "python", "python.tar.gz"), filepath.Join(cwd, "..", "payload", osName, "wheels")},
-			{filepath.Join(cwd, "..", "..", "payload", "darwin", "python", "python.tar.gz"), filepath.Join(cwd, "..", "..", "payload", "darwin", "wheels")},
+			{filepath.Join(cwd, "..", "..", "payload", osName, "python", "python.tar.gz"), filepath.Join(cwd, "..", "..", "payload", osName, "wheels")},
 		}
 		for _, c := range candidates {
 			if fileExists(c.t) && dirExists(c.w) {
@@ -712,7 +713,7 @@ func locateBundledPythonAssets() (tarball, wheelsDir string, err error) {
 		}
 	}
 
-	return "", "", fmt.Errorf("bundled python assets not found (tried .app Resources + payload/darwin)")
+	return "", "", fmt.Errorf("bundled python assets not found (tried .app Resources + same-dir + payload/%s)", runtime.GOOS)
 }
 
 // locateBundleBinDir 找 bundle 內的 bin 目錄（含 ffmpeg / yt-dlp / visiona-local-server）。
@@ -743,12 +744,13 @@ func locateBundleBinDir() (string, error) {
 		}
 	}
 
-	// 開發模式 fallback
+	// 開發模式 fallback（依 GOOS 挑對應 payload 子目錄）
 	if cwd, err := os.Getwd(); err == nil {
+		osName := runtime.GOOS // darwin / windows / linux
 		candidates := []string{
-			filepath.Join(cwd, "payload", "darwin", "bin"),
+			filepath.Join(cwd, "payload", osName, "bin"),
-			filepath.Join(cwd, "..", "payload", "darwin", "bin"),
+			filepath.Join(cwd, "..", "payload", osName, "bin"),
-			filepath.Join(cwd, "..", "..", "payload", "darwin", "bin"),
+			filepath.Join(cwd, "..", "..", "payload", osName, "bin"),
 		}
 		for _, c := range candidates {
 			if dirExists(c) {
@@ -1210,10 +1212,12 @@ func oldDataDirCandidates() []string {
 // locateServerBinary 找 visiona-local-server 執行檔。
 //
 // 搜尋順序：
-//  1. 與 Wails app 可執行檔同目錄（打包後的位置）
+//  1. 與 Wails app 可執行檔同目錄下的 bin/（Windows/Linux installer 佈局，Inno Setup .iss 裝到 {app}\bin）
-//  2. macOS app bundle 內：Contents/MacOS/ 或 Contents/Resources/
+//  2. 與 Wails app 可執行檔同目錄（開發/舊佈局）
-//  3. 開發模式：<repo>/dist/visiona-local-server（相對 cwd）
+//  3. macOS app bundle 內：Contents/Resources/bin 或 Contents/Resources
-//  4. 開發模式：<repo>/server/visiona-local-server
+//  4. 開發模式：<repo>/payload/<os>/bin/visiona-local-server
+//  5. 開發模式：<repo>/dist/visiona-local-server
+//  6. 開發模式：<repo>/server/visiona-local-server
 func locateServerBinary() (string, error) {
 	binName := "visiona-local-server"
 	if runtime.GOOS == "windows" {
@@ -1222,12 +1226,15 @@ func locateServerBinary() (string, error) {
 
 	candidates := []string{}
 
-	// 1. 與 Wails app 同目錄
+	// 1-2. 打包後佈局（installer 生成的目錄結構）
 	if exe, err := os.Executable(); err == nil {
 		exeDir := filepath.Dir(exe)
+		// {app}\bin\visiona-local-server.exe — Windows / Linux installer 標準佈局
+		candidates = append(candidates, filepath.Join(exeDir, "bin", binName))
+		// {app}\visiona-local-server.exe — exe 跟 server 同目錄的扁平佈局
 		candidates = append(candidates, filepath.Join(exeDir, binName))
 
-		// 2. macOS app bundle 常見位置
+		// 3. macOS app bundle 佈局
 		if runtime.GOOS == "darwin" {
 			candidates = append(candidates,
 				filepath.Join(exeDir, "..", "Resources", "bin", binName),
@@ -1237,9 +1244,12 @@ func locateServerBinary() (string, error) {
 		}
 	}
 
-	// 3-4. 開發模式
+	// 4-6. 開發模式
 	if cwd, err := os.Getwd(); err == nil {
+		osName := runtime.GOOS // darwin / windows / linux
 		candidates = append(candidates,
+			filepath.Join(cwd, "payload", osName, "bin", binName),
+			filepath.Join(cwd, "..", "payload", osName, "bin", binName),
 			filepath.Join(cwd, "dist", binName),
 			filepath.Join(cwd, "..", "dist", binName),
 			filepath.Join(cwd, "server", binName),