Add drag-and-drop GUI for the V3 spectral bypass

Small Tkinter app: drop images in, get SynthID-cleaned copies out,
with an option to strip EXIF/XMP/IPTC metadata from the output.
Runs offline on the existing V3 codebook, no PyTorch required.

gui/Launch SynthID Cleaner.command

@@ -0,0 +1,11 @@
+#!/bin/bash
+cd "$(dirname "$0")"
+if [ ! -d venv ]; then
+  python3 -m venv venv
+  source venv/bin/activate
+  pip install --quiet --upgrade pip
+  pip install --quiet -r requirements-gui.txt
+else
+  source venv/bin/activate
+fi
+python gui.py