[damarals]

Closes #31.

Summary

• Adds a new deckLibrary.updateName(id, name) method (mirrors the existing read-modify-write pattern used by updateYearOverride, gated by the per-key write lock).
• Adds an Ionicons ellipsis-vertical button to the unified deck page's headerRight, after the existing Export PDF button.
• Tapping the button opens a small drop-down menu with two actions: Rename deck and Delete deck.
• Rename opens a centered modal with a TextInput pre-filled with the current name, trims before commit, refuses empty input, and on success updates the in-screen state.deck so the header title re-renders without a full reload.
• Delete replicates the library long-press flow exactly (Alert.alert with destructive style, same copy), then deckLibrary.delete(id) and router.replace('/').

Test plan

• npm run typecheck — clean
• npm run lint — clean
• npm test — 145 pass (143 baseline + 2 new DeckLibrary.updateName tests)
• Manual: open a deck, tap the new menu, rename — header title and subtitle update without a reload
• Manual: open a deck, tap the menu, delete — confirmation matches library long-press, then returns to /
• Manual: rename to whitespace only — Save remains disabled