polish(engine): standard empty/loading/error states (Phase L)

New ui_modal::spawn_empty_state — glyph + headline + optional detail,
centred, with next-step actions composed alongside rather than
configured in. Glyphs restricted to FiraMono-covered ranges (suits,
arrows, ASCII) per the section-10/11 Android constraint.

Swept every improvised surface onto it:
- Theme store: loading / error / empty-catalog branches
- Leaderboard: fetching / error / be-the-first branches
- You-hub Replays tab: dedicated no-replays state (selector and
  actions no longer spawn dead controls when history is empty)
- Stats: first-launch nudge above the em-dash grid

The Account tab's sync row was deliberately NOT swept: it is a live
status + action row, not an empty state, and its deeper treatment
belongs to Phase M's sync-transparency work.

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

solitaire_engine/src/leaderboard_plugin.rs

@@ -24,13 +24,13 @@ use crate::font_plugin::FontResource;
 use crate::settings_plugin::{SettingsResource, SettingsStoragePath};
 use crate::sync_plugin::SyncProviderResource;
 use crate::ui_modal::{
-    ButtonVariant, ModalScrim, ScrimDismissible, spawn_modal, spawn_modal_actions,
-    spawn_modal_button, spawn_modal_header,
+    ButtonVariant, ModalScrim, ScrimDismissible, spawn_empty_state, spawn_modal,
+    spawn_modal_actions, spawn_modal_button, spawn_modal_header,
 };
 use crate::ui_theme::{
-    ACCENT_PRIMARY, BG_ELEVATED, BORDER_SUBTLE, RADIUS_SM, STATE_INFO, TEXT_DISABLED, TEXT_PRIMARY,
-    TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG, TYPE_CAPTION, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4,
-    Z_MODAL_PANEL, Z_PAUSE_DIALOG,
+    ACCENT_PRIMARY, BG_ELEVATED, BORDER_SUBTLE, RADIUS_SM, TEXT_DISABLED, TEXT_PRIMARY,
+    TEXT_SECONDARY, TYPE_BODY, TYPE_CAPTION, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4, Z_MODAL_PANEL,
+    Z_PAUSE_DIALOG,
 };
 
 // ---------------------------------------------------------------------------
@@ -536,11 +536,6 @@ fn spawn_leaderboard_screen(
             font_size: TYPE_CAPTION,
             ..default()
         };
-        let font_status = TextFont {
-            font: font_handle.clone(),
-            font_size: TYPE_BODY_LG,
-            ..default()
-        };
         let font_row = TextFont {
             font: font_handle.clone(),
             font_size: TYPE_BODY,
@@ -647,30 +642,31 @@ fn spawn_leaderboard_screen(
         .with_children(|body| {
             match data {
                 LeaderboardResource::Idle => {
-                    body.spawn((
-                        Text::new("Fetching\u{2026}"),
-                        font_status.clone(),
-                        TextColor(STATE_INFO),
-                    ));
+                    spawn_empty_state(
+                        body,
+                        "\u{21BB}",
+                        "Fetching the leaderboard\u{2026}",
+                        None,
+                        font_res,
+                    );
                 }
                 LeaderboardResource::Error(_) => {
-                    body.spawn((
-                        Text::new("Couldn't reach the leaderboard. Try again later."),
-                        font_status.clone(),
-                        TextColor(TEXT_SECONDARY),
-                    ));
+                    spawn_empty_state(
+                        body,
+                        "!",
+                        "Couldn't reach the leaderboard.",
+                        Some("Try again later."),
+                        font_res,
+                    );
                 }
                 LeaderboardResource::Loaded(rows) if rows.is_empty() => {
-                    body.spawn((
-                        Text::new("Be the first on the leaderboard."),
-                        font_status.clone(),
-                        TextColor(TEXT_PRIMARY),
-                    ));
-                    body.spawn((
-                        Text::new("Win a game and opt in to appear here."),
-                        font_row.clone(),
-                        TextColor(TEXT_SECONDARY),
-                    ));
+                    spawn_empty_state(
+                        body,
+                        "\u{2660}",
+                        "Be the first on the leaderboard.",
+                        Some("Win a game and opt in to appear here."),
+                        font_res,
+                    );
                 }
                 LeaderboardResource::Loaded(rows) => {
                     // Column headers