Fix clipboard copy on HTTP (non-secure) contexts, update docs

navigator.clipboard is undefined on non-HTTPS origins — add
execCommand fallback. Also sync CLAUDE.md with actual project
structure (Dockerfiles, nginx, CI, correct API/button descriptions).

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

frontend/src/App.tsx

@@ -29,7 +29,18 @@ function App() {
 
   const handleCopy = async (id: number) => {
     const text = await getEntryContent(id);
-    navigator.clipboard.writeText(text);
+    if (navigator.clipboard) {
+      await navigator.clipboard.writeText(text);
+    } else {
+      const textarea = document.createElement("textarea");
+      textarea.value = text;
+      textarea.style.position = "fixed";
+      textarea.style.opacity = "0";
+      document.body.appendChild(textarea);
+      textarea.select();
+      document.execCommand("copy");
+      document.body.removeChild(textarea);
+    }
   };
 
   return (