feat: add GET /libraries and library query param plumbing

New `/libraries` endpoint returns configured libraries so clients can
discover them. `FilesRequest` and `MemoriesRequest` gain an optional
`library` param (accepts name or numeric id). Unknown values are
rejected with 400; absent values span all libraries. `/memories`
now scopes its filesystem walk + EXIF query to the resolved library.
`MemoryItem` carries `library_id` so union-mode clients can render a
per-item source badge.

Behavior is unchanged in single-library mode: omitting `library` still
returns results from the primary library, which is the only one
configured until a second row is added to the libraries table.

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

src/memories.rs

@@ -107,6 +107,9 @@ pub struct MemoriesRequest {
     pub span: Option<MemoriesSpan>,
     /// Client timezone offset in minutes from UTC (e.g., -480 for PST, 60 for CET)
     pub timezone_offset_minutes: Option<i32>,
+    /// Optional library filter. Accepts a library id (e.g. "1") or name
+    /// (e.g. "main"). When omitted, results span all libraries.
+    pub library: Option<String>,
 }
 
 #[derive(Debug, Serialize, Clone)]
@@ -114,6 +117,9 @@ pub struct MemoryItem {
     pub path: String,
     pub created: Option<i64>,
     pub modified: Option<i64>,
+    /// Id of the library this memory belongs to. Allows clients to show a
+    /// per-item source badge in union mode.
+    pub library_id: i32,
 }
 
 #[derive(Debug, Serialize)]
@@ -417,6 +423,7 @@ fn collect_exif_memories(
                     path: file_path.clone(),
                     created,
                     modified,
+                    library_id: crate::libraries::PRIMARY_LIBRARY_ID,
                 },
                 file_date,
             ))
@@ -478,6 +485,7 @@ fn collect_filesystem_memories(
                         path: path_relative,
                         created,
                         modified,
+                        library_id: crate::libraries::PRIMARY_LIBRARY_ID,
                     },
                     file_date,
                 ))
@@ -526,7 +534,23 @@ pub async fn list_memories(
 
     debug!("Now: {:?}", now);
 
-    let base = Path::new(&app_state.base_path);
+    // Resolve the optional library filter. Unknown values are a 400; None
+    // means "all libraries" — currently equivalent to the primary library
+    // while only one is configured.
+    let library = match crate::libraries::resolve_library_param(
+        &app_state,
+        q.library.as_deref(),
+    ) {
+        Ok(lib) => lib,
+        Err(msg) => {
+            warn!("Rejecting /memories request: {}", msg);
+            return HttpResponse::BadRequest().body(msg);
+        }
+    };
+    // For Phase 3 the walker still operates against a single library's root.
+    // Multi-library union support for the filesystem walk comes in Phase 4.
+    let scoped_library = library.unwrap_or_else(|| app_state.primary_library());
+    let base = Path::new(&scoped_library.root_path);
 
     // Build the path excluder from base and env-configured exclusions
     let path_excluder = PathExcluder::new(base, &app_state.excluded_dirs);
@@ -535,7 +559,7 @@ pub async fn list_memories(
     let exif_memories = collect_exif_memories(
         &exif_dao,
         &span_context,
-        &app_state.base_path,
+        &scoped_library.root_path,
         now,
         span_mode,
         years_back,
@@ -546,12 +570,12 @@ pub async fn list_memories(
     // Build HashSet for deduplication
     let exif_paths: HashSet<PathBuf> = exif_memories
         .iter()
-        .map(|(item, _)| PathBuf::from(&app_state.base_path).join(&item.path))
+        .map(|(item, _)| PathBuf::from(&scoped_library.root_path).join(&item.path))
         .collect();
 
     // Phase 2: File system scan (skip EXIF files)
     let fs_memories = collect_filesystem_memories(
-        &app_state.base_path,
+        &scoped_library.root_path,
         &path_excluder,
         &exif_paths,
         now,
@@ -1098,6 +1122,7 @@ mod tests {
                     path: "photo1.jpg".to_string(),
                     created: Some(jan_15_2024_9am),
                     modified: Some(jan_15_2024_9am),
+                    library_id: crate::libraries::PRIMARY_LIBRARY_ID,
                 },
                 NaiveDate::from_ymd_opt(2024, 1, 15).unwrap(),
             ),
@@ -1106,6 +1131,7 @@ mod tests {
                     path: "photo2.jpg".to_string(),
                     created: Some(jan_15_2020_10am),
                     modified: Some(jan_15_2020_10am),
+                    library_id: crate::libraries::PRIMARY_LIBRARY_ID,
                 },
                 NaiveDate::from_ymd_opt(2020, 1, 15).unwrap(),
             ),
@@ -1114,6 +1140,7 @@ mod tests {
                     path: "photo3.jpg".to_string(),
                     created: Some(jan_16_2021_8am),
                     modified: Some(jan_16_2021_8am),
+                    library_id: crate::libraries::PRIMARY_LIBRARY_ID,
                 },
                 NaiveDate::from_ymd_opt(2021, 1, 16).unwrap(),
             ),