fix(theme): light-mode color polish + replace launcher icon

[dmnyc]

Summary

Three coupled changes that tidy up light mode and replace the
Android-Studio-default launcher icon. Companion doc
`LIGHT_MODE_COLOR_PARITY.md` describes the contract for the iOS agent
to mirror.

• Light-mode primary + zap animation (preserved from
  `fix/light-mode-theme-ui` — first commit) — deeper light-mode
  `primary` (`#D9730D` for the default theme; `darkenColor(..., 0.18)`
  for user-picked accents) so buttons keep contrast on near-white
  surfaces. New `zapAnimationColor` (saturation × 1.15, lightness ≥ 0.5)
  scoped to the in-flight bolt animation so the burst doesn't read
  muddy on light backgrounds. Static UI everywhere else continues to
  use plain `zapColor`.
• Throughout-the-theme orange consistency — light-mode `zapColor`
  and `bookmarkColor` now track `customLightPrimary`. The post-zap
  icon, post-zap count text, reaction count after react, top zap
  indicators in `NotificationsScreen`, wallet accents, and the
  Lightning QR icon all render the same orange as the rest of the
  theme. Previously these were pinned to `#B85C00` against a primary
  of `#D9730D`, producing a two-shade mismatch.
• Launcher icon — replaced the AS-default green-grid + droid icon
  with the iOS wisp artwork as a proper adaptive icon: vector
  foreground from the iOS SVG (radial-gradient orange wisp with eye
  cutouts via `evenOdd`), solid-black vector background. Group scaled
  to 65% so launcher masks (circle / squircle / rounded square / etc.)
  clip the padding rather than the wisp. Legacy bitmap fallbacks at
  every density were regenerated from the iOS-rendered Android PNGs.
• Cross-platform doc — `LIGHT_MODE_COLOR_PARITY.md` captures
  decisions: `zapColor == primary` in light mode,
  `zapAnimationColor == vivid(zapColor)` only for the animation, default
  theme `light.primary == #D9730D`. Includes a 4-step visual test and
  an iOS port checklist.

Test plan

• Switch to light mode (default theme). Confirm post-zap icon +
  count text on a previously-zapped post is `#D9730D` — the same
  orange as the Save / Connect / Confirm buttons elsewhere.
• Open Notifications → find a zap row — bolt + sat count are the
  same `#D9730D`.
• Open Wallet → Send/Receive button rings are the same `#D9730D`.
• Trigger a fresh zap on any post. In-flight bolt animation pulses
  a noticeably brighter orange (the `zapAnimationColor` vivid
  variant). Animation is never muddy or dark.
• Switch to dark mode. All colors unchanged from main (no
  regressions).
• Pick a non-default custom accent color (e.g. blue) in Theme
  Settings. Confirm light-mode buttons + zap icon both render the
  darkened variant (`darkenColor(accent, 0.18)`) and match each
  other.
• Try a non-default theme preset (Nord, Gruvbox, etc.) — their
  curated light-mode colors should remain unchanged.
• App launcher icon: home screen shows the orange wisp on black
  background (no green grid). Recents thumbnail matches. On a
  circular-mask launcher (Pixel) the wisp is fully visible — no
  cropping of its curl/outline.
• Splash screen on cold launch shows the wisp icon (same vector).