Initial commit: note-taking/task-tracking app with LLM integration scaffold

Vue 3 + TypeScript frontend with Pinia stores, markdown rendering (marked + DOMPurify),
wikilink/tag linkification, and autocomplete. Quart async backend with SQLAlchemy 2.0,
PostgreSQL ARRAY columns, task-note companion linking, backlinks, and note-to-task
conversion. Docker Compose setup with PostgreSQL 16 and Ollama.

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

frontend/src/composables/useTheme.ts

@@ -0,0 +1,29 @@
+import { ref } from "vue";
+
+type Theme = "light" | "dark";
+
+const theme = ref<Theme>(getInitialTheme());
+
+function getInitialTheme(): Theme {
+  const stored = localStorage.getItem("theme");
+  if (stored === "light" || stored === "dark") return stored;
+  if (window.matchMedia("(prefers-color-scheme: light)").matches) return "light";
+  return "dark";
+}
+
+function applyTheme(t: Theme) {
+  document.documentElement.setAttribute("data-theme", t);
+  localStorage.setItem("theme", t);
+}
+
+export function useTheme() {
+  // Apply on first use
+  applyTheme(theme.value);
+
+  function toggleTheme() {
+    theme.value = theme.value === "dark" ? "light" : "dark";
+    applyTheme(theme.value);
+  }
+
+  return { theme, toggleTheme };
+}