feat(ui): in dark mode, filled and floating buttons in cobalt itself, white on it

In dark mode the primary colour is cobalt lightened (#AEB9FF), readable as
text and thin marks on the dark surfaces, and filled buttons took it: Todo's
send button glared bright beside everything else; floating buttons took
Material's dark primary container. Both are cobalt itself now, white on it,
as in light mode (decision 6 of the developer's list, 9 Nov 2026); links,
tabs and switches keep the lighter tone. Filled icon buttons take no theme
of their own in Flutter (the icon buttons' theme is the plain ones' too),
so they take filledIconButtonStyle: Learn's study and send buttons,
Todo's send buttons and Locate me, Meditate's stop dictating.

Whats-New: In dark mode, filled buttons and the + button are cobalt with a white icon, no longer a bright light blue.
Whats-New-De: Im dunklen Modus sind gefüllte Schaltflächen und die +-Schaltfläche kobaltblau mit weißem Symbol statt grell hellblau.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/meditate/halkyon_meditate_flutter/lib/src/feature/journal/widget/dream_screen.dart

@@ -557,6 +557,7 @@ class const _DictationRow(
             children: [
               if (listening)
                 IconButton.filled(
+                  style: filledIconButtonStyle(context),
                   tooltip: l10n.dreamStopDictating,
                   icon: const Icon(LucideIcons.square),
                   onPressed: () => unawaited(dictation.stop()),