1055 User Search Toast Inline Messages Fix D17b6769

# User Search Toast and Inline Messages Fix

## Overview

Updated the `searchUsers()` function to use inline and toast messages instead of browser alert pop-ups, improving user experience and aligning with modern UI patterns.

**Version Implemented:** v0.237.001

**Related PR:** [#608](https://github.com/microsoft/simplechat/pull/608#discussion_r2701900020)

## Problem

The user search functionality in group management used browser `alert()` pop-ups for all feedback messages (empty search, no users found, errors). This created a disruptive user experience and was inconsistent with the toast notification patterns used elsewhere in the application.

## Solution

Refactored the `searchUsers()` function to display feedback using:
- **Inline messages**: Primary feedback shown directly in the search results area
- **Toast notifications**: Used only for errors, in addition to inline messaging

## User Experience

### Empty Search Query
When users click search without entering a query:
- Inline message displayed in the search results area
- No disruptive alert pop-up

### No Users Found
When the search returns no results:
- Informative inline message in the results area
- Clear indication that no matching users exist

### Users Found
When one or more users are found:
- Results displayed in the search results area
- Success feedback integrated naturally into the flow

### Error Handling
When an error occurs:
- Inline error message displayed
- Toast notification also shown for visibility
- Consistent with application error handling patterns

## Technical Details

### Files Modified
- Group management JavaScript (search user functionality)

### Changes
- Replaced `alert()` calls with inline message rendering
- Added toast notification for error cases only
- Maintained consistent styling with existing UI patterns

## Benefits

1. **Non-disruptive UX**: Users can continue working without dismissing pop-ups
2. **Contextual feedback**: Messages appear where users are looking (in the search area)
3. **Consistency**: Aligns with toast notification patterns used elsewhere
4. **Accessibility**: Better screen reader support with inline messages
5. **Modern UI**: Follows contemporary web application design patterns

## Testing

1. Open group management → Add Members
2. Click Search without entering a query → Verify inline "empty search" message
3. Search for a non-existent user → Verify inline "no users found" message
4. Search for an existing user → Verify results display correctly
5. Simulate network error → Verify both inline message and toast appear