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/bin/populate_knowledge.rs

@@ -185,6 +185,9 @@ async fn main() -> anyhow::Result<()> {
         Arc::new(Mutex::new(Box::new(SqliteKnowledgeDao::new())));
     let face_dao: Arc<Mutex<Box<dyn FaceDao>>> =
         Arc::new(Mutex::new(Box::new(SqliteFaceDao::new())));
+    let user_ai_prefs_dao: Arc<Mutex<Box<dyn image_api::database::UserAiPrefsDao>>> = Arc::new(
+        Mutex::new(Box::new(image_api::database::SqliteUserAiPrefsDao::new())),
+    );
     let persona_dao: Arc<Mutex<Box<dyn image_api::database::PersonaDao>>> = Arc::new(Mutex::new(
         Box::new(image_api::database::SqlitePersonaDao::new()),
     ));
@@ -208,6 +211,7 @@ async fn main() -> anyhow::Result<()> {
         face_dao,
         knowledge_dao,
         persona_dao,
+        user_ai_prefs_dao,
         all_libs.clone(),
     );