🤖 refactor: redesign Project Settings page (#1241)

## Summary

Redesigns the Project Settings section to match the visual patterns used
in GeneralSection and ProvidersSection.

## Changes

### Layout & Structure
- Row-based layout with labels/descriptions on left, controls on right
- Clear section headers with consistent typography
- Intro paragraph explaining where settings are stored

### Idle Compaction
- Replaced checkbox with Switch component (consistent with other
toggles)
- Clean two-row layout for enable toggle and hours threshold

### MCP Servers
- Cleaner card design using `bg-background-secondary`
- Error states and tool allowlist in bordered subsections
- Tighter action button grouping

### Add Server Form
- Converted to collapsible `<details>` element (reduces visual noise
when not adding)
- Accent-colored summary with chevron animation
- Smaller, consistently styled form inputs

### Styling Consistency
- `text-muted` for descriptions, `text-foreground` for labels
- `bg-modal-bg` and `focus:border-accent` for inputs
- Removed heavy borders and backgrounds

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_Generated with `mux` • Model: `anthropic:claude-opus-4-5` • Thinking:
`high`_

Author: ammar-agent