feat(icon): line-art cal + calendula bloom + numeral "1"

Replaces the simple numeral-only foreground from v0.1.0. The new mark
keeps the kalendae reference explicit (a bold "1" inside the
calendar body) and adds a small calendula bloom as a badge in the
bottom-right corner so the app's "calendula" brand reads at first
glance.

- design/icon/calendula_mark.svg: source SVG (232x232 viewport,
  monochrome, lawnicons-style strokes 12/8)
- app/src/main/res/drawable/ic_launcher_foreground.xml: regenerated
  as a VectorDrawable preserving the source path data. Off-white
  (#FAF6F0) strokes on the existing slate background. Reused as the
  <monochrome> slot so Android 13+ themed-icon launchers can recolor
  it from wallpaper.
- fdroid-metadata/.../{en-US,de-DE}/icon.png: 512x512 PNG composed
  from the same source SVG with the slate background baked in, so
  F-Droid clients show a fully rendered tile in the app catalog.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -19,6 +19,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Unit-Tests für Cursor-Mapping (alle §8-Defensiv-Cases), Repository-Flows mit Turbine, DataStore round-trip
 - Instrumented smoke test against the real CalendarContract provider
 
+### Changed
+- Redesigned launcher icon: line-art calendar with a stylized "1" inside
+  (kalendae reference) and a small calendula bloom badge in the
+  bottom-right corner. Replaces the simple "1"-only foreground from
+  v0.1.0. Source SVG checked in at `design/icon/calendula_mark.svg`,
+  also used to regenerate the F-Droid catalog `icon.png` (512x512)
+  per locale.
+
 ## [0.1.1] — 2026-06-08
 
 ### Fixed