chore: CLAUDE.md compliance — relative paths, CORS, README tech stack, .vch-description

- Fix absolute API paths in index.html (/analyze, /move, /preview → relative)
- Allow all CORS origins in server.py for reverse-proxy compatibility
- Add tech stack section to README.md
- Create .vch-description for VCH Showcase

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

index.html

@@ -218,7 +218,7 @@
     // --- Folder picker ---
     el("pick-btn").addEventListener("click", async () => {
       try {
-        const res = await fetch("/pick-folder");
+        const res = await fetch("pick-folder");
         if (res.status === 204) return;
         const data = await res.json();
         el("folder-input").value = data.folder;
@@ -250,7 +250,7 @@
 
       let data;
       try {
-        const res = await fetch("/analyze", {
+        const res = await fetch("analyze", {
           method: "POST",
           headers: { "Content-Type": "application/json" },
           body: JSON.stringify(payload),
@@ -285,7 +285,7 @@
     // --- Review ---
     function makeThumb(path, name) {
       const img = document.createElement("img");
-      img.src = "/preview?path=" + encodeURIComponent(path);
+      img.src = "preview?path=" + encodeURIComponent(path);
       img.alt = name;
       img.onerror = function() { this.style.display = "none"; };
       img.addEventListener("click", () => openLightbox(img.src, name));
@@ -380,7 +380,7 @@
       el("progress-label").textContent = "Verschiebe " + toMove.length + " Fotos...";
 
       try {
-        const res = await fetch("/move", {
+        const res = await fetch("move", {
           method: "POST",
           headers: { "Content-Type": "application/json" },
           body: JSON.stringify({ paths: toMove, folder: currentFolder }),