Add LLM tool calling for creating tasks, notes, and searching from chat

Ollama tool/function calling integration allows the LLM to create tasks,
create notes, and search existing notes on behalf of the user during chat.
Multi-round tool loop (max 5 rounds) lets the model execute tools then
produce a natural language response. Tool results are persisted in a new
JSONB column on messages and rendered as compact cards with linked titles.

- Migration 0013: add tool_calls JSONB column to messages
- New services/tools.py: tool definitions + execute_tool dispatcher
- llm.py: ChatChunk dataclass, stream_chat_with_tools(), date in system prompt
- generation_task.py: multi-round tool call loop with SSE tool_call events
- Frontend: ToolCallRecord type, streamingToolCalls in store, ToolCallCard
  component, rendering in ChatMessage and ChatView streaming bubble

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

frontend/src/views/ChatView.vue

@@ -7,6 +7,7 @@ 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";
 
 const route = useRoute();
@@ -400,6 +401,13 @@ function excludeAutoNote(noteId: number) {
                 <div class="message-header">
                   <span class="role-label">{{ settingsStore.assistantName }}</span>
                 </div>
+                <div v-if="store.streamingToolCalls.length" class="streaming-tool-calls">
+                  <ToolCallCard
+                    v-for="(tc, i) in store.streamingToolCalls"
+                    :key="i"
+                    :tool-call="tc"
+                  />
+                </div>
                 <div class="message-content prose" v-html="streamingRendered"></div>
                 <span class="typing-indicator"></span>
               </div>
@@ -690,6 +698,12 @@ function excludeAutoNote(noteId: number) {
   word-break: break-word;
 }
 
+.streaming-tool-calls {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.3rem;
+  margin-bottom: 0.4rem;
+}
 .typing-indicator {
   display: inline-block;
   width: 6px;