Restyle the watch app in the «Лес» palette with the Flutter app icon

- BalancePalette (Shared/AppTheme.swift): the palette of BalanceFlutter's
  default preset. Balance card in a green gradient with mint text, income
  teal (↙) and expense deep orange (↗) as in the Flutter app, mint accent
  and a forest «Добавить операцию» button instead of indigo/purple.
- Money shows no kopecks when whole, otherwise exactly two decimals
  («8 480,50 ₽»), like the Flutter client.
- App icon: same artwork as BalanceFlutter (branding/icon.svg), every
  size of AppIcon.appiconset rendered by the new branding/render.sh
  (resvg, bundled Roboto fonts).
- Repository avatar and README banner redrawn in the same style as the
  BalanceFlutter banner, with real simulator screenshots (docs/).

Checked on the watchOS 27.2 simulator (icon in the app grid, home and
accounts screens). Builds for simulator and device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

branding/render.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Re-renders the watch app icon (every size in AppIcon.appiconset), avatar.png
+# and banner.png from their SVG sources. Requires resvg
+# (https://github.com/linebender/resvg). Uses the bundled Roboto fonts, so the
+# result does not depend on system fonts. icon.svg is the same artwork as the
+# BalanceFlutter app icon (palette «Лес»).
+set -euo pipefail
+cd "$(dirname "${BASH_SOURCE[0]}")"
+fonts=(
+  --skip-system-fonts
+  --use-font-file fonts/Roboto-Regular.ttf
+  --use-font-file fonts/Roboto-Medium.ttf
+  --use-font-file fonts/Roboto-Bold.ttf
+)
+icons=../BalanceWatch/Assets.xcassets/AppIcon.appiconset
+for file in "$icons"/BalanceIcon-*.png; do
+  size="${file##*-}"; size="${size%.png}"
+  resvg -w "$size" -h "$size" icon.svg "$file"
+done
+resvg "${fonts[@]}" -w 512 -h 512 avatar.svg avatar.png
+resvg "${fonts[@]}" banner.svg banner.png