[BUG] [Dashboard] - Chat widget quick-action buttons do not produce AI response on -v2 deployment

## Bug Description

The dashboard chat widget (quick-action buttons and chat input) does not display AI responses when used on the `ca-ato-copilot-dashboard-v2` deployment. Clicking "📊 Portfolio overview" navigates the page but the chat panel never shows a response message. The `Send message` button remains disabled. The chat panel reverts to showing only the initial quick-action buttons with no conversation history.

## Steps to Reproduce

1. Navigate to `https://ca-ato-copilot-dashboard-v2.blackwater-9393aa1a.centralus.azurecontainerapps.io/`
2. In the Chat panel, click "📊 Portfolio overview"
3. Observe: page navigates/reloads but chat panel shows no response
4. Try typing in the chat input text box
5. Observe: Send button remains disabled

## Expected Behavior

- Clicking a quick-action button sends the message and the AI responds with portfolio summary data
- Chat input accepts text and Send button becomes enabled
- AI response appears in the chat panel

## Actual Behavior

- Quick-action buttons trigger page navigation but no chat message or AI response appears
- Chat panel resets to showing initial buttons with no conversation
- Send message button is always disabled
- Chat input textbox does not appear to accept text (Send never enables)

## Browser Console Errors

```
[2026-06-24T07:18:59.060Z] Error: Failed to start the HttpConnection before stop() was called.
```
(SignalR race condition — related to #544)

## Note on Related Issues

- This appears distinct from #425 ([CLOSED] Chat widget shows 'AI provider unreachable')
- #425 was filed against the `-st` deployment; this is against the `-v2` deployment
- The root cause may be the SignalR race condition (#544) preventing chat initialization
- Or the chat endpoint configuration may differ on -v2

## Browser/Environment
Dashboard: `ca-ato-copilot-dashboard-v2.blackwater-9393aa1a.centralus.azurecontainerapps.io`
Browser: Chromium (Playwright/Hermes)
Date: 2026-06-24
Sweep: Automated 4-hour QA sweep

## Playwright Test Code
```typescript
test('[Dashboard] Chat widget quick-action buttons produce AI response', async ({ page }) => {
await page.goto('/');
await page.click('button:has-text("📊 Portfolio overview")');
// Chat response should appear within 5 seconds
await expect(page.locator('.chat-message, [data-testid="chat-response"]')).toBeVisible({ timeout: 5000 });
});
```

*Filed by Oracle — Automated 4-hour QA Sweep 2026-06-24T07:17:52Z*