Add settings page, model management, and chat UX improvements

- Settings infrastructure: key-value settings table, GET/PUT API, Pinia store
- Configurable assistant name (default "Fable") in settings and LLM system prompt
- Model catalog with 18 models in 3 categories (General Purpose, Coding,
  Uncensored / Creative Writing) with download/select/remove functionality
- Move Ollama status indicator from chat views to global nav bar
- Chat bubble layout: user messages right-aligned, assistant left-aligned
- Floating dark input bar with auto-focus and circular send button
- Fix HTML entity rendering (' apostrophe issue in marked/DOMPurify pipeline)
- Fix new chat button navigation (fetchConversation before router.push)
- Recent chats section on home page with "New Chat" button
- Update summary.md with Phase 4.5 changes

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

frontend/src/App.vue

@@ -1,14 +1,18 @@
 <script setup lang="ts">
-import { ref, computed } from "vue";
+import { ref, computed, onMounted, onUnmounted } from "vue";
 import { useRoute } from "vue-router";
 import AppHeader from "@/components/AppHeader.vue";
 import ChatPanel from "@/components/ChatPanel.vue";
 import ToastNotification from "@/components/ToastNotification.vue";
 import { useTheme } from "@/composables/useTheme";
+import { useChatStore } from "@/stores/chat";
+import { useSettingsStore } from "@/stores/settings";
 
 useTheme();
 
 const route = useRoute();
+const chatStore = useChatStore();
+const settingsStore = useSettingsStore();
 const chatPanelOpen = ref(false);
 
 const contextNoteId = computed(() => {
@@ -24,6 +28,15 @@ const contextNoteId = computed(() => {
 function toggleChatPanel() {
   chatPanelOpen.value = !chatPanelOpen.value;
 }
+
+onMounted(() => {
+  chatStore.startStatusPolling();
+  settingsStore.fetchSettings();
+});
+
+onUnmounted(() => {
+  chatStore.stopStatusPolling();
+});
 </script>
 
 <template>