feat: Add streaming chat + scroll persistence; improve markdown & links

Backend
- /chat: support streaming via StreamingResponse; save full reply after stream ends. Non-stream path unchanged.
- ChatRequest: add stream flag (default false).
- GenerateTitleRequest: add model and use it instead of hardcoded llama3.
- ollama_client.chat_stream(): new async generator parsing Ollama streaming JSON (both formats).
- Remove response_model from /chat to allow streaming; non-stream still returns { reply }.

Electron
- Open external links in system browser (setWindowOpenHandler, shell.openExternal).
- New IPC: update-settings, open-external-link.
- Set minimum window size; preload exposes updateSettings and openExternalLink.

Frontend (React)
- Streaming UI with live chunking; sticky-bottom only when user at bottom.
- Per-session scroll persistence and robust restore.
- New message tip to jump to latest reply when scrolled up.
- Disable Send while sending; spinner.
- General Settings: stream output toggle; propagate model/stream changes.
- Apply color scheme at boot; extract colorSchemes helper.
- Sidebar UX tweaks and unread badges.

Markdown/rendering
- Code blocks: language title bar and wrapper.
- Tables: GitHub-style parsing, per-cell borders, rounded wrapper, spacing, alignment.
- Headings: remove blank line after h1-h4.
- <hr>: handle after tables; strip following whitespace.
- Links: target=_blank with icon and URL tooltip.

Styles
- Add styles for code/table wrappers, new-message tip, toggle, spinner; hover/active vars; narrower sidebar.

API notes / breaking changes
- /chat accepts stream=true and returns text/plain streamed chunks.
- generate-title now requires a model.
- Non-stream /chat response shape unchanged.

electron/main.cjs

@@ -1,5 +1,5 @@
 
-const { app, BrowserWindow, Menu, ipcMain } = require('electron')
+const { app, BrowserWindow, Menu, ipcMain, shell } = require('electron')
 const path = require('path')
 const { is } = require('@electron-toolkit/utils')
 const fs = require('fs')
@@ -44,6 +44,8 @@ async function createMainWindow () {
   mainWindow = new BrowserWindow({
     width: 1000,
     height: 720,
+    minWidth: 680,
+    minHeight: 300,
     show: false,
     webPreferences: {
       preload: path.join(__dirname, 'preload.cjs'),
@@ -62,6 +64,11 @@ async function createMainWindow () {
   } else {
     await mainWindow.loadFile(path.join(__dirname, '../dist/index.html'))
   }
+
+  mainWindow.webContents.setWindowOpenHandler(({ url }) => {
+    shell.openExternal(url);
+    return { action: 'deny' };
+  });
 }
 
 async function createSettingsWindow () {
@@ -166,6 +173,16 @@ ipcMain.handle('set-setting', (event, key, value) => {
   return true
 })
 
+ipcMain.handle('update-settings', (event, settings) => {
+  appSettings = { ...appSettings, ...settings }
+  saveSettings()
+  return true
+})
+
+ipcMain.on('open-external-link', (event, url) => {
+  shell.openExternal(url)
+})
+
 app.on('window-all-closed', () => {
   if (process.platform !== 'darwin') app.quit()
 })

electron/preload.cjs

@@ -4,5 +4,11 @@ const { contextBridge, ipcRenderer } = require('electron')
 // Expose a secure API to the renderer process
 contextBridge.exposeInMainWorld('electronAPI', {
   getSettings: () => ipcRenderer.invoke('get-settings'),
-  setSetting: (key, value) => ipcRenderer.invoke('set-setting', key, value)
+  setSetting: (key, value) => ipcRenderer.invoke('set-setting', key, value),
+  updateSettings: (settings) => ipcRenderer.invoke('update-settings', settings),
+  openExternalLink: (event) => {
+    event.preventDefault();
+    const url = event.currentTarget.href;
+    ipcRenderer.send('open-external-link', url);
+  }
 })