Enable thinking mode in full chat view, keep disabled in widget/panel

stream_chat_with_tools now accepts a think parameter. run_generation
forwards it to Ollama. The message POST route reads think from the
request body. ChatView passes think=true so qwen3 uses chain-of-thought
reasoning for full conversations; the dashboard widget and ChatPanel
omit it, staying fast. Dashboard button updated to "Think it through
in Chat →" to signal the deeper capability.

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

frontend/src/views/ChatView.vue

@@ -161,6 +161,7 @@ async function sendMessage() {
     content,
     contextNoteId,
     excludedNoteIds.value.size ? [...excludedNoteIds.value] : undefined,
+    true, // enable thinking in the full chat view
   );
   sending.value = false;