Polish dialog styles and button variants

[kmcginnes]

Description

Consistency pass across dialog footers, button variants, and the dialog overlay/scroll model.

Button changes:

• New outline-danger variant for destructive secondary actions (red text, danger-subtle hover, outlined border)
• outline and primary variants gain font-base for consistent weight

Dialog component changes:

• DialogBody now scrolls independently — header and footer stay fixed (matching AlertDialog)
• DialogOverlay lightened to 15% opacity and dialog content gets a stronger shadow for better separation
• DialogFooter gains bg-muted/50 background with top border

Usage updates across all dialogs:

• All secondary/default-variant buttons in dialog footers → outline
• Done/Save/Close action buttons → primary
• Reset to Default buttons → outline-danger
• CreateConnection restructured to render DialogBody/DialogFooter itself (was previously wrapped externally)
• Create Namespace dialog: added Cancel button, renamed Save to "Create Namespace", removed icon
• Raw Response dialog: Close button → primary, Copy to Clipboard → outline

How to read

1. packages/graph-explorer/src/components/Button/Button.tsx — the new outline-danger variant
2. packages/graph-explorer/src/components/Dialog.tsx — flex-col layout, scrollable body, overlay/footer styling
3. packages/graph-explorer/src/modules/CreateConnection/CreateConnection.tsx — restructured to own its DialogBody/DialogFooter
4. packages/graph-explorer/src/modules/NodesStyling/NodeStyleDialog.tsx — variant updates and form flex fix
5. Remaining files — same pattern: secondary → outline, add Cancel, etc.

Validation

• pnpm checks passes (types, lint, format)
• pnpm test passes — 31 dialog-rendering tests confirmed
• Visual: dialogs now scroll body content with pinned header/footer at short viewports
• Visual: overlay is lighter, footer has subtle background, buttons are visually consistent

Related Issues

• Closes Use DialogFooter in connection modal #1152
• Closes Clean up the node/edge style dialog: reset button, footer, and overlay #1912
• Related to Shared user styles #1896
• Related to Spike: visual redesign of the style dialogs #1885

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I have verified pnpm checks passes with no errors.
• I have verified pnpm test passes with no failures.
• I have covered new added functionality with unit tests if necessary.
• I have updated documentation if necessary.