Add CalDAV calendar integration, LLM-suggested tags, and settings refinements

- CalDAV integration: per-user calendar config, create/list/search events
  via caldav library, LLM tools for calendar operations from chat
- LLM-suggested tags: new tag_suggestions service prompts LLM with existing
  tags and note content to suggest 3-5 relevant tags; exposed via API
  endpoints (suggest-tags, append-tag); integrated into editor views
  (suggest button + clickable pills) and chat tool calls (pills in
  ToolCallCard with one-click apply)
- Settings/model UI refinements, generation task improvements

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

frontend/src/views/ChatView.vue

@@ -6,7 +6,6 @@ import { useSettingsStore } from "@/stores/settings";
 import { apiGet } from "@/api/client";
 import { renderMarkdown } from "@/utils/markdown";
 import ChatMessage from "@/components/ChatMessage.vue";
-import ModelSelector from "@/components/ModelSelector.vue";
 import ToolCallCard from "@/components/ToolCallCard.vue";
 import type { Note } from "@/types/note";
 
@@ -30,9 +29,6 @@ const noteSearchResults = ref<{ id: number; title: string }[]>([]);
 const noteSearchLoading = ref(false);
 let noteSearchTimer: ReturnType<typeof setTimeout> | null = null;
 
-// Model selection
-const selectedModel = ref("");
-
 // Exclude tracking (session-scoped per conversation)
 const excludedNoteIds = ref<Set<number>>(new Set());
 
@@ -76,12 +72,6 @@ onMounted(async () => {
   await store.fetchConversations();
   if (convId.value) {
     await store.fetchConversation(convId.value);
-    if (store.currentConversation?.model) {
-      selectedModel.value = store.currentConversation.model;
-    }
-  }
-  if (!selectedModel.value) {
-    selectedModel.value = store.defaultModel;
   }
   nextTick(() => inputEl.value?.focus());
 });
@@ -112,26 +102,6 @@ watch(convId, async (newId) => {
   nextTick(() => inputEl.value?.focus());
 });
 
-// Sync selectedModel from loaded conversation
-watch(
-  () => store.currentConversation?.model,
-  (model) => {
-    if (model) selectedModel.value = model;
-  }
-);
-
-// Persist model changes to backend
-watch(selectedModel, (newModel, oldModel) => {
-  if (
-    newModel &&
-    oldModel &&
-    newModel !== oldModel &&
-    store.currentConversation
-  ) {
-    store.updateConversationModel(store.currentConversation.id, newModel);
-  }
-});
-
 watch(
   () => store.streamingContent,
   () => scrollToBottom()
@@ -155,7 +125,7 @@ async function selectConversation(id: number) {
 }
 
 async function newConversation() {
-  const conv = await store.createConversation("", selectedModel.value);
+  const conv = await store.createConversation();
   await store.fetchConversation(conv.id);
   router.push(`/chat/${conv.id}`);
 }
@@ -344,10 +314,6 @@ function excludeAutoNote(noteId: number) {
               <line x1="3" y1="18" x2="21" y2="18"/>
             </svg>
           </button>
-          <ModelSelector
-            v-model="selectedModel"
-            :disabled="store.streaming"
-          />
           <h2>{{ store.currentConversation.title || "New Chat" }}</h2>
           <button
             v-if="store.currentConversation.messages.length"