fix: improve notifications styles

[marekdano]

Fixes four accessibility/consistency issues raised by @a-effort in review of #67 (tracked in #94).

• Badge success/warning contrast (AA): bg-success/15 text-success put green-600/amber-600 text on its own 15% tint, dropping success to 2.79:1 and warning to 2.71:1 in light mode (text-xs badge text needs 4.5:1). Added --success-foreground/--warning-foreground tokens at the 700 shades for light mode (dark mode already passed, so it reuses the existing 400 shades) and pointed the badge's success/warning variants at them, while text-success/text-warning stay on the 600/400 shades for icon-only usages.
• Two different reds in one form: BasicAuth.tsx, OAuth2Auth.tsx (8 occurrences), and CustomHeadersAuth.tsx used text-red-500 for required-field asterisks/errors while MCPServerForm.tsx and QueryParameterAuth.tsx used text-destructive. AdvancedSettings renders all of these as siblings, so both reds showed in the same form and diverged further in dark mode. All now use text-destructive.
• Three sibling preview panels missed the status-icon pass: ResourcePreviewResult.tsx, ToolPreviewResult.tsx, and
  ToolLiveInvokeResult.tsx still used raw lucide CheckCircle2/AlertCircle (ResourcePreviewResult also used text-emerald-500) instead of the STATUS_ICON/text-success treatment PromptPreviewResult already had. Brought all three in line.
• Info notifications dropped below AA: inline-notification.tsx applied STATUS_TONE_CLASS.info (text-muted-foreground) to both the icon and the message text, taking the message from 5.17:1 to 3.45:1 in light mode. The icon keeps the muted tone; the message now uses text-foreground.

Test plan

• npx vitest run — 3278 passed, 1 pre-existing skip
• npx eslint on changed files — clean
• npx prettier --check on changed files — clean
• npx tsc -b --noEmit — one pre-existing, unrelated error (ServerHandshakeRequest missing from generated types), confirmed present on
  main via git stash
• Updated inline-notification.test.tsx's info-type assertion from text-muted-foreground to text-foreground to match the fix

[a-effort]

Requesting one change, on the fourth item (info notification text):

The contrast figure behind it doesn't reproduce. --muted-foreground in light mode is oklch(0.556 0 0), which resolves to #737373; on --background that measures 4.74:1, not 3.45:1. The message is text-sm (14px, normal weight), so the bar is 4.5:1 and the existing styling already clears it. There is no AA problem to fix here.

Please drop from the PR:

• src/components/ui/inline-notification.tsx:36, back to <p className={text-sm ${toneClass}}>
• src/components/ui/inline-notification.test.tsx:57, assertion back to text-muted-foreground and the test name back to "neutral text"

My mistake; nice work! Test file I generated to take a look at changes, in case it's helpful for anyone:

color test.html