feat(todo): a pin in the map's middle, and what is around it (ADR 0033, D32)

The location picker fills the screen with its map, the search floating
over it. A pin stays in the middle, lifting while the map moves, as
Molly's; where it lands the instance names the address and lists the
places around, as Threema's. That is `nearby` on the search endpoint,
for those signed in, the point neither kept nor logged, counted among
the searches: two lookups, as a plain one finds house numbers alone.

Fixes the map's credit, which overflowed a phone and was pale on white.

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/todo/halkyon_todo_flutter/lib/l10n/app_de.arb

@@ -287,6 +287,9 @@
   "locationSearchFailed": "Die Suche hat nicht geklappt. Versuch es noch einmal.",
   "locationNoResults": "Nichts gefunden",
   "locationRecent": "Zuletzt verwendet",
+  "locationNearby": "Oder einen Ort in der Nähe wählen",
+  "locationZoomIn": "Vergrößern",
+  "locationZoomOut": "Verkleinern",
   "locationPin": "Gesetzter Ort",
   "locationName": "Name",
   "locationMine": "Mein Standort",