Unified NL search Phase 2: /photos/search/unified endpoint

Composes the two existing engines (Path A orchestration):
- Translate NL -> StructuredQuery via local LLM, respecting LLM_BACKEND
  (resolve_backend(Local) -> ollama or llama-swap; no hybrid).
- Forward-geocode the place name into a gps circle.
- Structured filters (tags/EXIF/geo/date/media) build a candidate set of EXIF
  rows; CLIP ranks within it, joined by content_hash. Degenerate cases match
  existing behavior: semantic-only -> plain CLIP; filters-only -> date-sorted.
- Echoes the interpreted query (incl. resolved place) for editable client chips.

Refactor: extracted reusable cores from clip_search (score_photos, resolve_hits,
parse_library_scope, score_error_response) shared by both endpoints. Removed the
Phase 1 allow-until-wired attributes now that nl_query + geo are consumed.

fmt + clippy clean; 23 backend tests pass (7 geo, 12 nl_query, 4 unified).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/main.rs

@@ -54,6 +54,7 @@ mod perceptual_hash;
 mod state;
 mod tags;
 mod thumbnails;
+mod unified_search;
 mod utils;
 mod video;
 mod watcher;
@@ -333,6 +334,13 @@ fn main() -> std::io::Result<()> {
                     web::resource("/photos/search")
                         .route(web::get().to(clip_search::search_photos)),
                 )
+                .service(
+                    // Unified natural-language search: LLM translates the
+                    // query into structured filters + a semantic term, then
+                    // filters constrain and CLIP ranks. See src/unified_search.rs.
+                    web::resource("/photos/search/unified")
+                        .route(web::get().to(unified_search::unified_search::<SqliteTagDao>)),
+                )
                 .service(web::resource("/file/move").post(move_file::<RealFileSystem>))
                 .service(handlers::image::get_image)
                 .service(handlers::image::upload_image)