UI/UX pass: readability, feedback, safer actions, DRK branding

Items 1–12 of the interface review:

- Larger UI font (UI_FONT_SIZE) across widgets, menus, dialogs, Treeview rows.
- DRK-red header bar; window title shows entry count; runtime-drawn red-cross
  icon (also written to data/icon.png for the launcher).
- Status bar colour-coded by severity; transient messages auto-clear after 8 s,
  queue-count messages stay.
- Tab 1: more form spacing, digits-only PLZ, explicit "Auswahl entfernen" +
  Delete key for queue rows, confirm on "Warteschlange leeren", modal on
  duplicate save.
- Tab 2: raw lat/lon columns replaced by one "Karte" column (checkmark / red
  "fehlt"); ▲/▼ arrow on the active sort column; hint line always shows the
  saved-entry count.
- "Karte öffnen" with no coordinates shows a dialog, not just a status line.
- Window size/position remembered between sessions (data/window.json).

Verified by building and driving the window under Homebrew Python 3.12 / Tk 9;
non-GUI smoke tests still pass. Docs updated (changelog, overview, improvements,
data-model, setup, dev-notes).

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

docs/changelog.md

@@ -2,6 +2,32 @@
 
 Notable changes to the app. Newest first.
 
+## 2026-09-07 — UI/UX pass
+
+A round of usability improvements aimed at the non-technical user
+(see [improvements.md](improvements.md#uiux-review-2026-09-07)).
+
+- **Larger UI font** (`UI_FONT_SIZE = 11`) applied to all default fonts, menus,
+  dialogs and the Treeview (taller rows).
+- **DRK-red header bar** with the app name; window title shows the total count
+  ("… · 142 Einsätze"); simple red-cross window icon drawn at runtime (also
+  written to `data/icon.png` for the launcher).
+- **Status bar** is now colour-coded by severity (grey/green/orange/red), and
+  transient messages auto-clear after 8 s back to a neutral state; queue-count
+  messages stay put.
+- **Tab 1:** more spacing in the form; PLZ field accepts digits only;
+  "+ Hinzufügen" is a solid button; explicit **"Auswahl entfernen"** button and
+  <kbd>Delete</kbd> key for queue rows; **"Warteschlange leeren"** now asks for
+  confirmation; **duplicate save shows a modal** (list + "trotzdem speichern?")
+  instead of a transient hint.
+- **Tab 2:** the raw `lat`/`lon` columns are replaced by a single **"Karte"**
+  column (`✓` / red `fehlt`); active sort column shows a ▲/▼ arrow; the hint
+  line always shows the saved-entry count.
+- **"Karte öffnen"** with no coordinates now shows a dialog, not just a status
+  line.
+- **Window size & position** are remembered between sessions
+  (`data/window.json`).
+
 ## 2026-09-07 — data safety, robustness, easier input
 
 Addressed the top three findings from [improvements.md](improvements.md).
@@ -43,5 +69,5 @@ Addressed the top three findings from [improvements.md](improvements.md).
 
 ### Verification
 Non-GUI smoke tests (helpers, `DataStore` backup/atomic/recovery, geocoder
-resilience) pass. **The GUI could not be run on the development Mac** — see
-[dev-notes.md](dev-notes.md).
+resilience) pass. The GUI now *can* be built and driven on the dev Mac via a
+Homebrew Python with Tk 9 — see [dev-notes.md](dev-notes.md).