Vamooses Endeavors

ADDED:
- Diminishing-returns step coloring on each task row. Repeatable initiative
  tasks show next-completion XP and coupon values tinted by where the next
  rep lands on Blizzard's authoritative DR curve (curve 87592, decoded from
  DB2): #1 (100%) pale yellow → #2 (90%) → #3 (80%) → #4 (70%) → #5 (60%) →
  #6+ (50%) bright red floor. Single tasks have no DR coloring.
- Tooltip DR breakdown for repeatable tasks: hover any task to see base
  reward and a per-step list of all 6 dampening rungs (XP and coupons),
  with the current step marked. Coloring matches the row tint.
- Coupon forecast: each row's coupon badge now shows the dampened forecast
  for the next completion, computed from the same DR curve. Blizzard's
  GetQuestRewardCurrencyInfo returns BASE only — VE multiplies by the
  appropriate DR factor so the displayed value matches what you'll
  actually receive.

CHANGED:
- `EndeavorTracker:CalculateNextContribution` is now deterministic: trusts
  Blizzard's `task.progressContributionAmount` (already the dampened
  forecast) instead of waiting for an empirical floor to be observed.
- Schema migration v4 clears the now-orphaned `VE_DB.taskActualCoupons`
  table from existing saves.
- Live-refresh listener for the Endeavors tab now filters on the correct
  Store action names (`SET_TASKS`, `SET_ENDEAVOR_INFO`, `SET_HOUSE_LEVEL`).
  Previous code referenced two non-existent action names so endeavor-info
  updates never refreshed the visible tab.

FIXED:
- Tasks now refresh visibly within ~0.3s of completing one. Previously the
  Endeavors tab stayed stuck on the prior completion's values until you
  switched tabs, /reloaded, or zoned out and back. Three layered bugs all
  contributed (missing INITIATIVE_TASK_COMPLETED refetch, incomplete
  cache hash, broken live-refresh listener); all three now fixed.
- DR colors on dark themes are readable. The earlier dark-red floor step
  (L*≈42) failed WCAG body-text contrast; switched to a luminance-lifted
  YlOrRd ramp ending in bright red rather than deep red.

REMOVED (dead code now that the DR curve is authoritative):
- `buildTaskRules` + `self.taskRules` — ~60 lines of empirical floor-detection
  scaffolding that watched the activity log to learn each task's floor.
- `COMPLETIONS_TO_FLOOR` constant.
- The `actual or base` branch in `GetTaskCouponReward` and the
  `taskActualCoupons` per-task coupon history.
- `Tracker:GetAccountCompletionCount` + `self.accountCompletions` +
  `buildAccountCompletions` helper — only callers fed the now-redundant
  `_completions` arg of `CalculateNextContribution`.
- `_completions` arg on `CalculateNextContribution`.