Add EXIF search infrastructure (Phase 1 & 2)

Implements foundation for EXIF-based photo search capabilities:

- Add geo.rs module with GPS distance calculations (Haversine + bounding box)
- Extend FilesRequest with EXIF search parameters (camera, GPS, date, media type)
- Add MediaType enum and DateTakenAsc/DateTakenDesc sort options
- Create date_taken index migration for efficient date queries
- Implement ExifDao methods: get_exif_batch, query_by_exif, get_camera_makes
- Add FileWithMetadata struct for date-aware sorting
- Implement date sorting with filename extraction fallback
- Make extract_date_from_filename public for reuse

Next: Integrate EXIF filtering into list_photos() and enhance get_all_tags()

src/data/mod.rs

@@ -109,6 +109,8 @@ pub enum SortType {
     NameDesc,
     TagCountAsc,
     TagCountDesc,
+    DateTakenAsc,
+    DateTakenDesc,
 }
 
 #[derive(Deserialize)]
@@ -120,6 +122,23 @@ pub struct FilesRequest {
     pub tag_filter_mode: Option<FilterMode>,
     pub recursive: Option<bool>,
     pub sort: Option<SortType>,
+
+    // EXIF-based search parameters
+    pub camera_make: Option<String>,
+    pub camera_model: Option<String>,
+    pub lens_model: Option<String>,
+
+    // GPS location search
+    pub gps_lat: Option<f64>,
+    pub gps_lon: Option<f64>,
+    pub gps_radius_km: Option<f64>,
+
+    // Date range filtering (Unix timestamps)
+    pub date_from: Option<i64>,
+    pub date_to: Option<i64>,
+
+    // Media type filtering
+    pub media_type: Option<MediaType>,
 }
 
 #[derive(Copy, Clone, Deserialize, PartialEq, Debug)]
@@ -128,6 +147,14 @@ pub enum FilterMode {
     All,
 }
 
+#[derive(Copy, Clone, Deserialize, PartialEq, Debug)]
+#[serde(rename_all = "lowercase")]
+pub enum MediaType {
+    Photo,
+    Video,
+    All,
+}
+
 #[derive(Copy, Clone, Deserialize, PartialEq, Debug)]
 #[serde(rename_all = "lowercase")]
 pub enum PhotoSize {