fix(dates): prefer earliest of fs created/modified as fallback

On copied or restored files (e.g. a backup library), the OS stamps
created at copy time while modified is preserved from the source, so
the earlier of the two is a better proxy for when the content
originated. Adds utils::earliest_fs_time and threads it through the
three spots that fall back to filesystem dates: photos-list sort,
memories grouping, and insight-generation timestamp.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/files.rs

@@ -15,6 +15,7 @@ use crate::database::ExifDao;
 use crate::file_types;
 use crate::geo::{gps_bounding_box, haversine_distance};
 use crate::memories::extract_date_from_filename;
+use crate::utils::earliest_fs_time;
 use crate::{AppState, create_thumbnails};
 use actix_web::web::Data;
 use actix_web::{
@@ -138,8 +139,8 @@ fn in_memory_date_sort(
                     lib_roots.get(&lib_id).and_then(|root| {
                         let full_path = Path::new(root).join(&f.file_name);
                         std::fs::metadata(full_path)
-                            .and_then(|md| md.created().or(md.modified()))
                             .ok()
+                            .and_then(|md| earliest_fs_time(&md))
                             .map(|system_time| {
                                 <SystemTime as Into<DateTime<Utc>>>::into(system_time).timestamp()
                             })