Switch read paths to the true-instant date contract (ticket #119)

- New src/date_view.rs: pure read-side functions (row_true_instant,
  row_display_wall, row_display_day, filename_true_instant) applying the
  per-source convention table for unconverted rows and the new-contract
  triple for converted rows (ADR-0001).
- /memories: grouping on the row's true instant rendered in the owner's
  display zone (prefs -> app default), not the client device offset.
  SQL is a coarse interval pre-filter over the full years-back window;
  exact month-day/week/month matching across past years happens in Rust
  (memories::day_in_span, sqlite_w_week).
- Reels: ReelSelector::Memories carries an IANA display_tz instead of a
  fixed minute offset; pre-gen params read REEL_PREGEN_DISPLAY_TZ; the
  tz_offset_minutes ledger column stores the zone offset at render time.
- Insights: prompt-facing dates render as the display wall; the
  proximity timestamp and chat context block use the true instant;
  InsightGenerator reads the owner's display zone from prefs per call.
- GpsPhotoSummary carries the new-contract triple alongside the frozen
  legacy date_taken.

Closes #119

src/files.rs

@@ -1142,12 +1142,25 @@ pub async fn get_gps_summary(
         Ok(gps_data) => {
             let mut photos: Vec<GpsPhotoSummary> = gps_data
                 .into_iter()
-                .map(|(path, lat, lon, date_taken)| GpsPhotoSummary {
-                    path,
-                    lat,
-                    lon,
-                    date_taken,
-                })
+                .map(
+                    |(
+                        path,
+                        lat,
+                        lon,
+                        date_taken,
+                        date_utc,
+                        camera_offset_minutes,
+                        date_taken_tz_source,
+                    )| GpsPhotoSummary {
+                        path,
+                        lat,
+                        lon,
+                        date_taken,
+                        date_utc,
+                        camera_offset_minutes,
+                        date_taken_tz_source,
+                    },
+                )
                 .collect();
 
             // Sort by date_taken based on request, defaulting to ascending (oldest to newest)
@@ -1695,7 +1708,18 @@ mod tests {
             _context: &opentelemetry::Context,
             _base_path: &str,
             _recursive: bool,
-        ) -> Result<Vec<(String, f64, f64, Option<i64>)>, DbError> {
+        ) -> Result<
+            Vec<(
+                String,
+                f64,
+                f64,
+                Option<i64>,
+                Option<i64>,
+                Option<i32>,
+                Option<String>,
+            )>,
+            DbError,
+        > {
             todo!()
         }
 
@@ -1817,10 +1841,11 @@ mod tests {
             &mut self,
             _context: &opentelemetry::Context,
             _library_id: i32,
-            _span_token: &str,
-            _years_back: i32,
-            _tz_offset_minutes: i32,
-        ) -> Result<Vec<(String, i64, i64)>, DbError> {
+            _conv_lo: i64,
+            _conv_hi: i64,
+            _unconv_lo: i64,
+            _unconv_hi: i64,
+        ) -> Result<Vec<crate::database::models::ImageExif>, DbError> {
             Ok(Vec::new())
         }