Replace hardcoded toast styles with Bootstrap classes

[Copilot]

This PR addresses the issue where toast notifications were using hardcoded CSS values that conflicted with the existing Bootstrap 3 backend design. The problem was that the toast notifications forced specific green colors, rounded corners, and heavy shadows that didn't integrate well with custom backend themes.

Changes Made

JavaScript (assets/js/bloecks.js):

• Removed hardcoded inline styles for background, color, border-radius, and box-shadow
• Replaced with Bootstrap alert classes: alert-success, alert-warning, alert-danger, alert-info
• Updated close button to use Bootstrap's standard markup with class="close"
• Preserved essential animation and positioning styles

CSS (assets/css/bloecks.css):

• Removed hardcoded background colors from .bloecks-toast-* classes
• Eliminated border-radius: 8px as requested
• Removed box-shadow that conflicted with backend design
• Simplified padding to Bootstrap's default 15px
• Let Bootstrap alert classes handle all color and styling

Visual Comparison

The before section shows the old hardcoded approach with forced green colors and styling. The after section demonstrates the new Bootstrap-integrated approach that respects the existing theme framework.

Benefits

• ✅ No more hardcoded colors that conflict with backend themes
• ✅ Removed forced border-radius for cleaner integration
• ✅ Eliminated heavy box-shadow that disrupted design consistency
• ✅ Uses Bootstrap's semantic alert classes for proper color handling
• ✅ Maintains all existing functionality while improving theme compatibility

The toast notifications now properly integrate with Bootstrap 3 and will adapt to any custom backend styling without forcing unwanted visual overrides.

Fixes #161.

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