feat(home): presence selector as a compact dropdown instead of 3 radios

Replace the three tooltip'd presence radios in the home Friends card with a
pick_list dropdown + a one-line explainer for the current choice, mirroring the
Settings NetworkMode picker. Add PresenceMode::ALL + a Display impl (descriptive
labels) to back the picker. Tightens the Friends card vertically. clippy
--all-targets clean, 256 lib tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -1453,19 +1453,21 @@ fn friends_panel(state: &AppState) -> Element<'_, AppMessage> {
     .spacing(0)
     .width(iced::Length::Fill);
 
-    // Presence posture radios (each with a hover explainer).
-    let presence_radio = |mode: PresenceMode, label: &'static str| -> Element<'_, AppMessage> {
-        tooltip(
-            radio(label, mode, Some(state.config.presence_mode), AppMessage::PresenceModeSelected),
-            container(text(presence_mode_hint(mode)).size(11).color(color_text))
-                .padding(8)
-                .max_width(300.0)
-                .style(c_style(color_crust, color_surface, 6.0)),
-            iced::widget::tooltip::Position::Bottom,
+    // Presence posture: a compact dropdown (mirrors the Settings NetworkMode
+    // picker) with a one-line explainer for the current choice below it.
+    let presence_picker = column![
+        pick_list(
+            &PresenceMode::ALL[..],
+            Some(state.config.presence_mode),
+            AppMessage::PresenceModeSelected,
         )
-        .gap(8)
-        .into()
-    };
+        .width(iced::Length::Fill),
+        text(presence_mode_hint(state.config.presence_mode))
+            .size(11)
+            .color(color_subtext),
+    ]
+    .spacing(4)
+    .width(iced::Length::Fill);
 
     container(
         column![
@@ -1481,9 +1483,7 @@ fn friends_panel(state: &AppState) -> Element<'_, AppMessage> {
             add_form,
             vertical_space(14.0),
             text("Your presence").size(13).color(color_subtext),
-            presence_radio(PresenceMode::Normal, "Normal — friends only"),
-            presence_radio(PresenceMode::Invisible, "Invisible — appear offline"),
-            presence_radio(PresenceMode::Discoverable, "Discoverable — findable after a move"),
+            presence_picker,
         ]
         .spacing(6),
     )