chore: draw shared code from floret-kit (fresh re-migration onto current main)

Supersedes the stale chore/floret-kit-core-time branch: re-applies the
floret-kit migration on top of current main (122 commits ahead of the old
branch's base), pinning the kit at the multi-value-reminders + pinned-picker HEAD.

- Submodule + composite build (includeBuild), 6 module deps, CI submodules:
  recursive, reproducible-release scan extended to the kit, F-Droid recipe.
- Deletes the inline copies now owned by the kit (GroupedList, Picker scaffolds,
  InlineTextField, OptionCard, DialogControls, CrashReporter + dialog/submit,
  OnboardingScaffold, AppLanguage, TimeBridge, ReorderableColumn, DebugRibbon)
  and redraws them from components/identity/core-crash/core-locale/core-time.
- Reminder overrides drawn from core-reminders (multi-value ReminderOverride +
  codec); Calendula keeps its app-specific bits (all-day resolution, labels,
  presets, the multi-select ReminderDefaultPicker, its own CrashReportActivity).
- Theme draws FloretExpressiveTheme while keeping the user-typography param.

Build pending (deferred): run ./gradlew :app:compileDebugKotlin with ANDROID_HOME
(or floret-kit/local.properties) set.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "floret-kit"]
+	path = floret-kit
+	url = https://gitea.jeanlucmakiola.de/makiolaj/floret-kit.git