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/NoteEditorView.vue

@@ -5,6 +5,7 @@ import { useNotesStore } from "@/stores/notes";
 import { useToastStore } from "@/stores/toast";
 import { renderMarkdown } from "@/utils/markdown";
 import { useAssist } from "@/composables/useAssist";
+import { apiPost } from "@/api/client";
 import type { Editor } from "@tiptap/vue-3";
 import MarkdownToolbar from "@/components/MarkdownToolbar.vue";
 import TiptapEditor from "@/components/TiptapEditor.vue";
@@ -55,6 +56,41 @@ function truncateTarget(text: string, max = 60): string {
   return first.length > max ? first.slice(0, max) + "..." : first;
 }
 
+// Tag suggestions
+const suggestedTags = ref<string[]>([]);
+const appliedTags = ref<Set<string>>(new Set());
+const suggestingTags = ref(false);
+
+async function fetchTagSuggestions() {
+  if (suggestingTags.value) return;
+  suggestingTags.value = true;
+  suggestedTags.value = [];
+  appliedTags.value = new Set();
+  try {
+    const res = await apiPost<{ suggested_tags: string[] }>("/api/notes/suggest-tags", {
+      title: title.value,
+      body: body.value,
+    });
+    suggestedTags.value = res.suggested_tags;
+  } catch {
+    toast.show("Failed to get tag suggestions", "error");
+  } finally {
+    suggestingTags.value = false;
+  }
+}
+
+function applyTagSuggestion(tag: string) {
+  if (appliedTags.value.has(tag)) return;
+  body.value = body.value.trimEnd() + `\n#${tag}`;
+  appliedTags.value.add(tag);
+  markDirty();
+}
+
+function dismissTagSuggestions() {
+  suggestedTags.value = [];
+  appliedTags.value = new Set();
+}
+
 // Track saved state for dirty detection
 let savedTitle = "";
 let savedBody = "";
@@ -178,6 +214,25 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
         @input="markDirty"
       />
 
+      <div class="tag-suggest-row">
+        <button class="btn-suggest-tags" @click="fetchTagSuggestions" :disabled="suggestingTags">
+          {{ suggestingTags ? "Suggesting..." : "Suggest tags" }}
+        </button>
+        <template v-if="suggestedTags.length > 0">
+          <button
+            v-for="tag in suggestedTags"
+            :key="tag"
+            :class="['tag-pill', { applied: appliedTags.has(tag) }]"
+            :disabled="appliedTags.has(tag)"
+            @click="applyTagSuggestion(tag)"
+          >
+            #{{ tag }}
+            <span v-if="appliedTags.has(tag)" class="tag-check">&#10003;</span>
+          </button>
+          <button class="btn-dismiss-tags" @click="dismissTagSuggestions">&times;</button>
+        </template>
+      </div>
+
       <div class="editor-tabs">
         <button
           :class="['tab', { active: !showPreview }]"
@@ -385,6 +440,69 @@ onUnmounted(() => window.removeEventListener("beforeunload", onBeforeUnload));
   background: var(--color-bg-card);
 }
 
+/* ── Tag suggestions ── */
+.tag-suggest-row {
+  display: flex;
+  flex-wrap: wrap;
+  align-items: center;
+  gap: 0.4rem;
+}
+.btn-suggest-tags {
+  padding: 0.3rem 0.7rem;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-sm);
+  background: var(--color-bg-card);
+  color: var(--color-text-secondary);
+  cursor: pointer;
+  font-size: 0.8rem;
+}
+.btn-suggest-tags:hover:not(:disabled) {
+  border-color: var(--color-primary);
+  color: var(--color-primary);
+}
+.btn-suggest-tags:disabled {
+  opacity: 0.6;
+  cursor: wait;
+}
+.tag-pill {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.2rem;
+  padding: 0.2rem 0.55rem;
+  border: 1px solid var(--color-primary);
+  border-radius: 999px;
+  background: transparent;
+  color: var(--color-primary);
+  font-size: 0.8rem;
+  cursor: pointer;
+  transition: background 0.15s, color 0.15s;
+}
+.tag-pill:hover:not(:disabled) {
+  background: var(--color-primary);
+  color: #fff;
+}
+.tag-pill.applied {
+  background: var(--color-success, #2ecc71);
+  border-color: var(--color-success, #2ecc71);
+  color: #fff;
+  cursor: default;
+}
+.tag-check {
+  font-size: 0.7rem;
+}
+.btn-dismiss-tags {
+  padding: 0.1rem 0.4rem;
+  border: none;
+  background: none;
+  color: var(--color-text-muted);
+  cursor: pointer;
+  font-size: 1rem;
+  line-height: 1;
+}
+.btn-dismiss-tags:hover {
+  color: var(--color-text);
+}
+
 /* ── Assist panel ── */
 .assist-panel {
   flex: 0 0 33.33%;