feat(dates): calendar-day date filters in the owner's display zone (#152)

/photos, /photos/exif and unified search take date_from_day /
date_to_day (YYYY-MM-DD): the server turns them into the first day's
start and the last day's end in the owner's display zone, the same days
/memories groups by. Each replaces its instant counterpart. Clients stop
computing midnights in the device's zone, which drifted by the travel
offset whenever the phone's zone differed from display_tz.

e2e check: every fixture is included by its display-zone day and
excluded by the days either side.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/unified_search.rs

@@ -77,6 +77,10 @@ pub struct UnifiedQuery {
     pub media_type: Option<MediaType>,
     pub date_from: Option<i64>,
     pub date_to: Option<i64>,
+    /// Calendar days (`YYYY-MM-DD`) in the owner's display zone; each
+    /// replaces its instant counterpart (see `date_view::apply_day_bounds`).
+    pub date_from_day: Option<String>,
+    pub date_to_day: Option<String>,
     pub camera_make: Option<String>,
     pub camera_model: Option<String>,
     pub gps_lat: Option<f64>,
@@ -292,6 +296,14 @@ pub async fn unified_search<TagD: TagDao>(
     tag_dao: Data<Mutex<TagD>>,
     query: Query<UnifiedQuery>,
 ) -> HttpResponse {
+    let mut query = query.into_inner();
+    crate::date_view::apply_day_bounds(
+        &mut query.date_from,
+        &mut query.date_to,
+        query.date_from_day.as_deref(),
+        query.date_to_day.as_deref(),
+        || crate::date_view::owner_display_zone(&state.user_ai_prefs_dao),
+    );
     let nl = query.q.trim().to_string();
     if nl.is_empty() {
         return bad_request("query parameter `q` is required");