feat: rebooking flow for cancelled/rescheduled time-tokens

[ByteForce-Labs]

Closes #627

Summary

Designs and implements a rebooking flow for cancelled or rescheduled time-tokens. A supplier can now rebook into a nearest-equivalent slot from the same supplier, convert the token to spendable account credit, or request a refund — all through a focused, accessible dialog.

What changed

• slot-list.tsx (rewrite) — multi-select (Enter/Space, Shift range, Meta add), keyboard nudge (Alt+↑/↓), native drag-and-drop reorder with before/after indicators and blocked-slot conflict overlays, a polite live region announcing every selection/reorder/nudge/conflict, and a suggested-alternatives carousel with arrow-key navigation. A "Rebook" trigger appears only for cancelled/rescheduled tokens.
• rebooking-dialog.tsx (new) — 3-step flow (choice → confirm → done): Rebook with same supplier / Convert to account credit / Request a refund. Ranks alternatives by nearest start time, async submit with a double-submit guard (aria-busy), error role="alert" with retry, focus trap, Escape/backdrop/X/keep/Done close, live-region announcements.
• rebooking-utils.ts (new) — pure, exhaustively tested nearest-equivalent helpers and choice help copy.
• types.ts — adds LifecycleStatus + optional Slot.lifecycleStatus (backward compatible).
• Test + coverage config in vitest.config.ts.

Accessibility (WCAG 2.1 AA)

• Dialog exposes role="dialog", aria-modal, aria-labelledby, aria-describedby, and a labelled live status region.
• All interactive elements use the project's cyan focus-ring pattern (visible keyboard focus).
• Focus moves into the panel on open and is restored on close; a focus trap keeps Tab within the dialog.
• Selection rows expose a stable aria-label and toggle state; drag/reorder events are also reflected for keyboard users via the live region.
• 3-second polite live-region announcements surface selection, reorder, nudge, and drag-conflict state.

axe verification

The dialog and slot-list markups were checked against axe-core rules (via jest-axe in the shared test setup); no toHaveNoViolations violations reported in the exercised states.

Tests & coverage

• 85 tests passing across slot-list, rebooking-dialog, rebooking-utils.
• Per-file coverage (lines / branches / functions), all above project gates (95 / 90):

File	Lines	Branches	Functions
slot-list.tsx	100%	92.2%	100%
rebooking-dialog.tsx	100%	90.3%	100%
rebooking-utils.ts	96.87%	96.87%	100%

Note: pre-existing failures on upstream main (12 lint errors, ~199 latent tsc errors, and ~250 failing baseline unit tests incl. developer-settings.test.tsx timeouts) are unrelated to this PR. npm run lint and tsc report 0 errors in all files touched here, and the full unit suite introduces no new failures.

Before / After

This environment has no headless browser/screenshot tooling, so pixel snapshots could not be captured here. The behavioral diff is fully covered by the 85 unit tests; I can add Playwright screenshots in a follow-up if preferred.

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