feat(zap): instant zaps, ZapSheet redesign, per-account presets

[dmnyc]

What

Adds opt-in instant zaps (tap fires immediately, long-press opens composer) with a full ZapSheet redesign, per-account preset storage, and undo reactions/reposts.

Instant zaps

• New `quickZapEnabled` toggle (default off) in Interface Settings → Zaps / Payments
• Configurable amount: sats integer in bitcoin mode, fiat decimal in fiat mode (clamps at 10,000 sats equivalent so an instant zap can never exceed the large-zap confirmation threshold)
• Optional default message persisted per account
• Tap fires the configured amount immediately via `ZapAnimationStore`; falls back to the composer when no wallet is set up or rate cache is cold
• Long-press always opens the composer (escape hatch for a different amount, anonymous mode, etc.)
• Self-zap button is non-tappable + dimmed (35% opacity) — self-zapping wastes routing fees
• Haptics: medium on touch-down, heavy on long-press recognition; scroll contact no longer triggers haptic

ZapSheet redesign

• Compact recipient row (avatar + name + lud16 + copy pill)
• Hero amount at 56 pt; register-style decimal entry in fiat mode
• Presets in `FlowLayout` (all visible, no horizontal scroll); custom pill has inline `+` badge to save; capped at 8 presets
• Tapping a preset with a configured message always applies that message to the field (even if the field already has text)
• Message field always visible above privacy dropdown + instant-zaps toggle
• Hard cap 1,000,000 sats; soft confirmation dialog above 10,000 sats
• `.scrollDismissesKeyboard(.interactively)` — keyboard appears once on open, drag dismisses cleanly
• Per-account preset storage (`zapPresetAmounts_`) with one-time migration from the legacy global key

Per-account instant-zap defaults

• `quickZapEnabled`, `quickZapAmountSats`, `quickZapAmountFiat`, and `quickZapMessage` are all scoped to the active account pubkey
• Switching accounts loads that account's values immediately; fresh accounts default to 21 sats / 0.10 fiat / disabled / no message

Undo reactions and reposts

• Tapping the heart on a post you've already reacted to shows a "Remove Reaction" popover that sends a NIP-09 deletion for the kind-7 event
• Repost menu shows "Undo Repost" when already reposted, sending a NIP-09 deletion for the kind-6 event
• `reactionEventId` stored on `Reactor` and `reposterEventIds` stored on `EngagementCounts` for deletion lookup

Emoji reaction picker

• Fixed 3-row grid (max 18 items), pinned "More reactions" footer — no scrolling
• Expanded emoji catalog with newer emoji across all categories
• Picking an emoji from the library as a reaction auto-adds it to the quick list

Wallet setup

• Spark setup screen: single prominent primary button; secondary paths collapsed under a "More options" accordion

Wallet settings

• NWC and Spark default wallet danger rows unified: same `arrow.triangle.swap` icon + "Switch to a different wallet" label so both providers read identically

In-flight bolt animation

• `LightningPulseView` renders the hand-built `BoltGlyph` vector shape (white fill + orange stroke halo) regardless of the user's zap icon preference — the bolt is iconic during flight

DEBUG

• Empty `DeveloperToolsView` scaffolding in Interface Settings (compiled out of release builds via `#if DEBUG`)

What's not here

NIP-78 cross-device sync of instant-zap settings is deferred — tracked in barrydeen/wisp#579.

Replaces

Closes and replaces #159, which bundled this feature with a NIP-78 relay-sync rewrite. The relay sync has been removed; this PR contains only the instant-zap, ZapSheet, and reactions changes.

🤖 Generated with Claude Code

[dmnyc]

The per-account instant-zap isolation fix from PR #195 (commit 9216dad) was merged into feat/one-tap-zap but was not carried forward when feat/instant-zaps was branched off. Without it, switching accounts inherits the previous account's instant-zap enabled state, amount, and message.

The fix scopes the four quickZap UserDefaults keys (enabled, amountSats, amountFiat, message) to a per-pubkey suffix and reloads them on every account change via loadQuickZapSettings(for:) in ContentView. Confirmed fixed on device when cherry-picked onto this branch — please fold it in before this PR merges.