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/stores/settings.ts

@@ -0,0 +1,69 @@
+import { ref, computed } from "vue";
+import { defineStore } from "pinia";
+import { apiGet, apiPut, apiPost } from "@/api/client";
+import type { AppSettings } from "@/types/settings";
+
+export const useSettingsStore = defineStore("settings", () => {
+  const settings = ref<AppSettings>({});
+  const loading = ref(false);
+  const installedModels = ref<string[]>([]);
+
+  const assistantName = computed(
+    () => settings.value.assistant_name || "Fable"
+  );
+
+  const defaultModel = computed(
+    () => settings.value.default_model || ""
+  );
+
+  async function fetchSettings() {
+    loading.value = true;
+    try {
+      settings.value = await apiGet<AppSettings>("/api/settings");
+    } catch {
+      // Use defaults on error
+    } finally {
+      loading.value = false;
+    }
+  }
+
+  async function updateSettings(updates: AppSettings) {
+    loading.value = true;
+    try {
+      settings.value = await apiPut<AppSettings>("/api/settings", updates);
+    } finally {
+      loading.value = false;
+    }
+  }
+
+  async function fetchInstalledModels() {
+    try {
+      const data = await apiGet<{ models: { name: string }[] }>("/api/chat/models");
+      installedModels.value = data.models.map((m) => m.name);
+    } catch {
+      installedModels.value = [];
+    }
+  }
+
+  async function pullModel(model: string) {
+    await apiPost("/api/chat/models/pull", { model });
+  }
+
+  async function deleteModel(model: string) {
+    await apiPost("/api/chat/models/delete", { model });
+    await fetchInstalledModels();
+  }
+
+  return {
+    settings,
+    loading,
+    installedModels,
+    assistantName,
+    defaultModel,
+    fetchSettings,
+    updateSettings,
+    fetchInstalledModels,
+    pullModel,
+    deleteModel,
+  };
+});