[BUG] [Remediation] - Create Remediation Task dialog closes silently but task is not persisted — zero feedback on failure

## Bug Description

The **"Create Remediation Task"** dialog on the Remediation Tasks page submits (dialog closes) but the task is **silently not created**. After clicking "Create Task" with valid required fields filled in, the dialog closes but:
- The task counter remains at "0"
- The task table still shows "No remediation tasks found."
- No success toast/notification appears
- No error message is shown

The failure is completely silent — the user has no indication whether submission succeeded or failed.

## Steps to Reproduce

1. Navigate to any system's remediation page (e.g., `/systems/b4d0aca6-cdb1-4630-84ae-df93b2747178/remediation`)
2. Click **"+ Create Task"** button
3. In the dialog, fill in:
- **Severity**: Medium (default)
- **Control ID**: `AC-2`
- **Task Title**: `QA Test Task - AC-2 Implementation` (required)
- Leave Description and Due Date blank
4. Click **"Create Task"** button
5. **Observe:** Dialog closes — verify task count and task table

## Expected Behavior

- Dialog closes after successful submission
- Task counter increments from 0 to 1
- New task appears in the task table with the provided title/control/severity
- Optional: Success toast notification shown

## Actual Behavior

- Dialog closes after ~1 second (appears to submit)
- Task counter remains at **0**
- Task table still shows **"No remediation tasks found."**
- No success or error feedback displayed anywhere
- Refreshing the page confirms the task was not persisted

## Screenshot

After dialog closes: TOTAL TASKS shows 0, task table shows "No remediation tasks found."

## Console Errors

No new JS errors observed from this specific interaction.

## Browser/Environment

Azure Container Apps Dashboard (flankspeed org-centric v2)
Browser: Chromium (Playwright/Hermes browser)
Date: 2026-07-07
System: QA Test System 2026-06-25T17:48:00Z (ID: b4d0aca6-cdb1-4630-84ae-df93b2747178)
Sweep: Automated 4-hour QA sweep

## Playwright Test Code

```typescript
test('[Remediation] Create Task successfully persists task', async ({ page }) => {
await page.goto('/systems/b4d0aca6-cdb1-4630-84ae-df93b2747178/remediation');
await page.click('button:has-text("Create Task")');
await page.fill('input[placeholder="e.g. AC-2"]', 'AC-2');
await page.fill('input[placeholder="Describe the remediation task"]', 'Test task for QA');
await page.click('dialog button:has-text("Create Task")');
// Verify task was created
await expect(page.locator('text=TOTAL TASKS').locator('..').locator('p').nth(1)).toContainText('1');
await expect(page.locator('table')).toContainText('Test task for QA');
});
```

## Related Issues

- #576 — MCP Kanban board remediation task intents return 'An error occurred'
- Distinct from API failures — this is the UI form submission pathway

*Filed by Oracle — Automated 4-hour QA Sweep 2026-07-07T09:11:00Z*