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/components/AppHeader.vue

@@ -0,0 +1,67 @@
+<script setup lang="ts">
+import { useTheme } from "@/composables/useTheme";
+
+const { theme, toggleTheme } = useTheme();
+</script>
+
+<template>
+  <header class="app-header">
+    <nav class="nav">
+      <router-link to="/" class="nav-brand">Fabled Assistant</router-link>
+      <div class="nav-links">
+        <router-link to="/notes" class="nav-link">Notes</router-link>
+        <router-link to="/tasks" class="nav-link">Tasks</router-link>
+        <button class="theme-toggle" @click="toggleTheme" :title="`Switch to ${theme === 'dark' ? 'light' : 'dark'} mode`">
+          {{ theme === "dark" ? "\u2600" : "\u263E" }}
+        </button>
+      </div>
+    </nav>
+  </header>
+</template>
+
+<style scoped>
+.app-header {
+  background: var(--color-bg-secondary);
+  border-bottom: 1px solid var(--color-border);
+}
+.nav {
+  max-width: 960px;
+  margin: 0 auto;
+  padding: 0.5rem 1rem;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+}
+.nav-brand {
+  font-weight: 700;
+  font-size: 1.1rem;
+  color: var(--color-primary);
+  text-decoration: none;
+}
+.nav-links {
+  display: flex;
+  align-items: center;
+  gap: 1rem;
+}
+.nav-link {
+  color: var(--color-text-secondary);
+  text-decoration: none;
+  font-size: 0.95rem;
+}
+.nav-link:hover {
+  color: var(--color-primary);
+}
+.theme-toggle {
+  background: none;
+  border: 1px solid var(--color-border);
+  border-radius: 4px;
+  padding: 0.25rem 0.5rem;
+  cursor: pointer;
+  font-size: 1.1rem;
+  color: var(--color-text);
+  line-height: 1;
+}
+.theme-toggle:hover {
+  background: var(--color-bg-card);
+}
+</style>