Remove numeric task shortcuts from kanban cards

[bborn]

What

Removes the little numbers (1–9, 11–99) shown on the right side of each kanban card, and the matching numeric keypress that jumped to a task in the selected column. Per the task: never used them, never pressed them to jump.

Changes

• renderTaskCard: dropped the shortcutHint param and its right-aligned indicator
• Desktop + mobile board views: removed shortcutNum tracking / TaskShortcutHint calls
• Removed KanbanBoard.SelectByShortcut
• Removed TaskShortcutHint / TaskIndexFromShortcut helpers (styles.go)
• app.go: removed the 1–9 (and double-digit 11/22/…) keypress handler, pendingShortcutDigit/shortcutTimeout state, and the shortcutTimeoutMsg tick/type
• Removed the associated tests

The #<id> task ID on the left of each card is untouched — only the right-side jump shortcuts are gone.

Verification

• go build ./... ✅
• go test ./internal/ui/ ✅
• golangci-lint run ./internal/ui/ → 0 issues ✅

🤖 Generated with Claude Code

[bborn]

QA — verified on isolated TUI instance

Seeded 12 backlog tasks and rendered the board (VHS, correctly-sized headless terminal) on main vs this branch, plus a functional check of the removed keypress.

Before (main) — numbers 1–7 on the right of each card

After (this branch) — no numbers

Functional checks (driven via --debug-state-file)

• Number key no longer jumps. Top card #12 selected → pressed 3 → state unchanged (view: dashboard, selected: 12). On main this jumped to the 3rd card and opened its detail view.
• Normal nav intact. Down moved selection #12 → #11; Enter opened the detail view (view: detail).
• go build ./..., go test ./internal/ui/, and golangci-lint run ./internal/ui/ all pass.

The #<id> on the left of each card is unchanged — only the right-side jump shortcuts (display + keypress) were removed.