compact filter row with bottom sheet for source/follows/sort

Replaces the two-row, mixed-control filter UI under the search bar with a
single segmented row for scope (All/People/Notes) and a Tune icon button
that opens a ModalBottomSheet containing Source, Follows-only, and Sort
controls. A primary-color dot on the icon indicates non-default filter
state.

Also renames SearchSortOrder.DEFAULT_EVENT/DEFAULT_PEOPLE to
EVENT_DEFAULT/PEOPLE_DEFAULT for consistency with EVENT_OPTIONS/
PEOPLE_OPTIONS, and routes the sheet's reset button through these
canonical constants so the UI default cannot drift from the ViewModel.

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/search/AdvancedSearchBarState.kt

@@ -84,10 +84,10 @@ class AdvancedSearchBarState(
     val noteResults: StateFlow<ImmutableList<Event>> = _noteResults.asStateFlow()
 
     // Sort orders
-    private val _eventSortOrder = MutableStateFlow(SearchSortOrder.DEFAULT_EVENT)
+    private val _eventSortOrder = MutableStateFlow(SearchSortOrder.EVENT_DEFAULT)
     val eventSortOrder: StateFlow<SearchSortOrder> = _eventSortOrder.asStateFlow()
 
-    private val _peopleSortOrder = MutableStateFlow(SearchSortOrder.DEFAULT_PEOPLE)
+    private val _peopleSortOrder = MutableStateFlow(SearchSortOrder.PEOPLE_DEFAULT)
     val peopleSortOrder: StateFlow<SearchSortOrder> = _peopleSortOrder.asStateFlow()
 
     // Derived sorted results
@@ -266,8 +266,8 @@ class AdvancedSearchBarState(
         _peopleResults.value = persistentListOf()
         _noteResults.value = persistentListOf()
         _relayStates.value = persistentListOf()
-        _eventSortOrder.value = SearchSortOrder.DEFAULT_EVENT
-        _peopleSortOrder.value = SearchSortOrder.DEFAULT_PEOPLE
+        _eventSortOrder.value = SearchSortOrder.EVENT_DEFAULT
+        _peopleSortOrder.value = SearchSortOrder.PEOPLE_DEFAULT
         activeSubIds.value = emptySet()
         eventDeduplicator.clear()
     }

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/search/SearchSortOrder.kt

@@ -34,7 +34,7 @@ enum class SearchSortOrder(
     companion object {
         val EVENT_OPTIONS = listOf(RELEVANCE, NEWEST, POPULAR)
         val PEOPLE_OPTIONS = listOf(NAME_AZ, NAME_ZA)
-        val DEFAULT_EVENT = NEWEST
-        val DEFAULT_PEOPLE = NAME_AZ
+        val EVENT_DEFAULT = NEWEST
+        val PEOPLE_DEFAULT = NAME_AZ
     }
 }