feat: content-hash-aware tag/insight sharing + library scoping

Tags and insights now follow content across libraries via content_hash
lookups on the read path, so the same file indexed at different rel_paths
in multiple libraries shares its annotations. Recursive tag search scopes
hits to the selected library by checking each tagged rel_path against
the library's disk (with a content-hash sibling fallback so tags attached
under one library's rel_path still match a content-equivalent file in
another). The /image and /image/metadata handlers fall back across
libraries when the file isn't under the resolved one, so union-mode
search results (which carry no library attribution in the response)
still serve correctly.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/main.rs

@@ -118,7 +118,25 @@ async fn get_image(
         }
     };
 
-    if let Some(path) = is_valid_full_path(&library.root_path, &req.path, false) {
+    // Union-mode search returns flat rel_paths with no library attribution,
+    // so clients may request a file under the wrong library. Try the
+    // resolved library first; if the file isn't there, fall back to any
+    // other library holding that rel_path on disk.
+    let resolved = is_valid_full_path(&library.root_path, &req.path, false)
+        .filter(|p| p.exists())
+        .map(|p| (library, p))
+        .or_else(|| {
+            app_state.libraries.iter().find_map(|lib| {
+                if lib.id == library.id {
+                    return None;
+                }
+                is_valid_full_path(&lib.root_path, &req.path, false)
+                    .filter(|p| p.exists())
+                    .map(|p| (lib, p))
+            })
+        });
+
+    if let Some((library, path)) = resolved {
         let image_size = req.size.unwrap_or(PhotoSize::Full);
         if image_size == PhotoSize::Thumb {
             let relative_path = path
@@ -207,9 +225,9 @@ async fn get_image(
         span.set_status(Status::error("Not found"));
         HttpResponse::NotFound().finish()
     } else {
-        span.set_status(Status::error("Bad photos request"));
-        error!("Bad photos request: {}", req.path);
-        HttpResponse::BadRequest().finish()
+        span.set_status(Status::error("Not found"));
+        error!("Path does not exist in any library: {}", req.path);
+        HttpResponse::NotFound().finish()
     }
 }
 
@@ -294,7 +312,23 @@ async fn get_file_metadata(
     let span_context =
         opentelemetry::Context::new().with_remote_span_context(span.span_context().clone());
 
-    let full_path = is_valid_full_path(&app_state.base_path, &path.path, false);
+    let library = libraries::resolve_library_param(&app_state, path.library.as_deref())
+        .ok()
+        .flatten()
+        .unwrap_or_else(|| app_state.primary_library());
+
+    // Fall back to other libraries if the file isn't under the resolved one,
+    // matching the `/image` handler so union-mode search results resolve.
+    let full_path = is_valid_full_path(&library.root_path, &path.path, false)
+        .filter(|p| p.exists())
+        .or_else(|| {
+            app_state.libraries.iter().find_map(|lib| {
+                if lib.id == library.id {
+                    return None;
+                }
+                is_valid_full_path(&lib.root_path, &path.path, false).filter(|p| p.exists())
+            })
+        });
 
     match full_path
         .ok_or_else(|| ErrorKind::InvalidData.into())