Release v3.1.0: native address search, guided first-run setup

## New
- Native in-device address search for setting your exact location,
  using the free OpenStreetMap Nominatim geocoding service - no more
  relying on imprecise IP-based location. Reachable both during
  first-time setup and anytime via Location Presets ("+").
- Guided first-time setup flow: language selection, followed by an
  optional location setup step (skippable) that explains why exact
  coordinates give a much better experience than automatic IP-based
  location, and a final setup-complete screen confirming everything
  is saved and ready.

## Improved
- The address search keyboard now shows a format hint (e.g. "Main
  Street 12, 12345 Springfield") and includes punctuation keys
  (comma, hyphen, slash, period, apostrophe) so addresses with house
  numbers like "45/3" can actually be entered.
- The preset-naming screen (when adding a location preset) now shows
  example names (e.g. "Home, Work, Holiday home") so new users
  understand what's being asked for.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/config.h

@@ -6,7 +6,7 @@ namespace Config {
     // CLAUDE.md-Workflow "Standard-Workflow: Push & Release") - erscheint
     // im Info-Screen (Menue > System > Info) und muss zum jeweiligen
     // Git-Tag passen.
-    constexpr const char* APP_VERSION = "3.0.1";
+    constexpr const char* APP_VERSION = "3.1.0";
 
     // Display-Helligkeit (Menue > System > Helligkeit), in Prozent.
     // MIN bewusst nicht 0 - ein komplett dunkles Display koennte sonst wie