Initial commit: prompt template manager

React + Tailwind frontend, FastAPI backend, settings.json storage.
Supports preset CRUD, live variable filling, and AI rewrite via OpenAI.

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

frontend/src/lib/parseVars.js

@@ -0,0 +1,19 @@
+const VAR_RE = /\{\{([a-zA-Z_][a-zA-Z0-9_]*)\}\}/g
+
+export function parseVars(template) {
+  const seen = new Set()
+  const vars = []
+  let m
+  VAR_RE.lastIndex = 0
+  while ((m = VAR_RE.exec(template)) !== null) {
+    if (!seen.has(m[1])) {
+      seen.add(m[1])
+      vars.push(m[1])
+    }
+  }
+  return vars
+}
+
+export function fillTemplate(template, values) {
+  return template.replace(/\{\{([a-zA-Z_][a-zA-Z0-9_]*)\}\}/g, (_, k) => values[k] ?? `{{${k}}}`)
+}