feat: FFmpeg GUI desktop application

Wails v2 + Vue3 + Go project with:
- Encode/Remux/Subtitle burn with hardware acceleration
- Real-time progress with ffmpeg stderr parsing (\r delimiter handling)
- Task queue with cancel support
- Per-task log viewer with color-coded output
- Custom frameless window with resize support
- Dark/light theme toggle
- Hardware encoder detection (NVENC/QSV/AMF)

internal/platform/windows.go

@@ -0,0 +1,70 @@
+//go:build windows
+
+package platform
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+var (
+	user32   = syscall.NewLazyDLL("user32.dll")
+	kernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+	setWindowLong            = user32.NewProc("SetWindowLongW")
+	getWindowLong            = user32.NewProc("GetWindowLongW")
+	setWindowPos             = user32.NewProc("SetWindowPos")
+	enumWindows              = user32.NewProc("EnumWindows")
+	getWindowThreadProcessId = user32.NewProc("GetWindowThreadProcessId")
+	getCurrentProcessId      = kernel32.NewProc("GetCurrentProcessId")
+)
+
+const (
+	GWL_STYLE        = ^uintptr(15) // -16
+	WS_THICKFRAME    = 0x00040000
+	WS_MAXIMIZEBOX   = 0x00010000
+	WS_MINIMIZEBOX   = 0x00020000
+	SWP_FRAMECHANGED = 0x0020
+	SWP_NOMOVE       = 0x0002
+	SWP_NOSIZE       = 0x0001
+	SWP_NOZORDER     = 0x0004
+	SWP_NOACTIVATE   = 0x0010
+)
+
+var mainHwnd uintptr
+
+// EnableResizeBorder re-adds the WS_THICKFRAME style to
+// the frameless Wails window so it can be resized from edges.
+func EnableResizeBorder() {
+	pid, _, _ := getCurrentProcessId.Call()
+
+	// Find our main window by enumerating top-level windows
+	cb := syscall.NewCallback(func(hwnd uintptr, lparam uintptr) uintptr {
+		var wpid uintptr
+		getWindowThreadProcessId.Call(hwnd, uintptr(unsafe.Pointer(&wpid)))
+		if wpid == pid {
+			// Check if it's a visible owned window (not a child/message-only)
+			style, _, _ := getWindowLong.Call(hwnd, GWL_STYLE)
+			if style&0x10000000 != 0 && style&0x40000000 == 0 { // WS_VISIBLE && !WS_CHILD
+				mainHwnd = hwnd
+				return 0 // stop enumeration
+			}
+		}
+		return 1 // continue
+	})
+	enumWindows.Call(cb, 0)
+
+	if mainHwnd == 0 {
+		return
+	}
+
+	style, _, _ := getWindowLong.Call(mainHwnd, GWL_STYLE)
+	newStyle := style | WS_THICKFRAME | WS_MAXIMIZEBOX | WS_MINIMIZEBOX
+	setWindowLong.Call(mainHwnd, GWL_STYLE, newStyle)
+	setWindowPos.Call(mainHwnd, 0, 0, 0, 0, 0,
+		SWP_FRAMECHANGED|SWP_NOMOVE|SWP_NOSIZE|SWP_NOZORDER|SWP_NOACTIVATE)
+
+	// Log for debugging
+	os.Stdout.WriteString("[platform] WS_THICKFRAME enabled on frameless window\n")
+}