Add search autocomplete and fix search state restoration

- Add SuggestFromList with Himalaya keywords for search input autocomplete
- Cache and restore metadata_by_id when cancelling search (fixes navigation)
- Set search_mode=True when opening panel for consistent Escape behavior
- Fix SearchPanel CSS vertical alignment with explicit heights

src/mail/app.py

@@ -77,6 +77,7 @@ class EmailViewerApp(App):
     search_query: Reactive[str] = reactive("")  # Current search filter
     search_mode: Reactive[bool] = reactive(False)  # True when showing search results
     _cached_envelopes: List[Dict[str, Any]] = []  # Cached envelopes before search
+    _cached_metadata: Dict[int, Dict[str, Any]] = {}  # Cached metadata before search
 
     def get_system_commands(self, screen: Screen) -> Iterable[SystemCommand]:
         yield from super().get_system_commands(screen)
@@ -917,6 +918,8 @@ class EmailViewerApp(App):
         if not search_panel.is_visible:
             # Cache current envelopes before searching
             self._cached_envelopes = list(self.message_store.envelopes)
+            self._cached_metadata = dict(self.message_store.metadata_by_id)
+            self.search_mode = True
             search_panel.show(self.search_query)
 
     def on_search_panel_search_requested(
@@ -938,11 +941,14 @@ class EmailViewerApp(App):
         self.search_mode = False
         self.search_query = ""
 
-        # Restore cached envelopes
+        # Restore cached envelopes and metadata
         if self._cached_envelopes:
             self.message_store.envelopes = self._cached_envelopes
             self._cached_envelopes = []
-            self._populate_list_view()
+        if self._cached_metadata:
+            self.message_store.metadata_by_id = self._cached_metadata
+            self._cached_metadata = {}
+        self._populate_list_view()
 
         # Restore envelope list title
         sort_indicator = "↑" if self.sort_order_ascending else "↓"