feat: lightbox EXIF panel, tag management, reorderable albums

EXIF info panel:
- New on-demand get_image_exif command (kamadak-exif) returning camera/lens/
  aperture/shutter/ISO/focal-length and decimal GPS; read from the file when the
  lightbox opens (no DB schema change, works on already-indexed images).
- Lightbox shows a Camera panel; GPS opens the location in the browser via
  OpenStreetMap (adds opener:allow-open-url capability).

Tag management:
- Backend rename_tag (rename, or merge when the target exists) and delete_tag
  (library-wide), both clearing the tag-cloud cache; store actions invalidate
  tag caches, refresh Explore, and re-point/refresh an active tag-search.
- Explore -> Tag Cloud gains a Manage mode: a flat list with per-tag rename/
  merge/delete.

Albums:
- Drag-to-reorder in the sidebar via framer-motion Reorder with a hover handle;
  order persists through the existing reorder_albums command.

Reads live store order on drag end and robustly derives GPS hemisphere from raw
EXIF ref bytes (review follow-ups). CHANGELOG updated.

src/store.ts

@@ -189,6 +189,19 @@ export interface Album {
   updated_at: string;
 }
 
+export interface ImageExif {
+  make: string | null;
+  model: string | null;
+  lens: string | null;
+  iso: string | null;
+  f_number: string | null;
+  exposure_time: string | null;
+  focal_length: string | null;
+  datetime_original: string | null;
+  gps_lat: number | null;
+  gps_lon: number | null;
+}
+
 export interface TagCloudEntry {
   count: number;
   representative_image_id: number;
@@ -551,6 +564,9 @@ interface GalleryState {
   getImageTags: (imageId: number) => Promise<ImageTag[]>;
   addUserTag: (imageId: number, tag: string) => Promise<ImageTag>;
   removeTag: (tagId: number) => Promise<void>;
+  getImageExif: (imageId: number) => Promise<ImageExif>;
+  renameTag: (from: string, to: string) => Promise<void>;
+  deleteTag: (tag: string) => Promise<number>;
 
   // Gallery multi-select (Feature A)
   toggleGallerySelected: (imageId: number) => void;
@@ -2210,6 +2226,47 @@ export const useGalleryStore = create<GalleryState>((set, get) => ({
     set({ exploreTagsFolderId: undefined });
   },
 
+  getImageExif: async (imageId) => {
+    return invoke<ImageExif>("get_image_exif", { params: { image_id: imageId } });
+  },
+
+  renameTag: async (from, to) => {
+    await invoke("rename_tag", { params: { from, to } });
+    // Tag content changed — invalidate the explore-tags and tag-cloud caches.
+    set({
+      exploreTagsFolderId: undefined,
+      exploreTagEntries: [],
+      tagCloudFolderId: undefined,
+      tagCloudEntries: [],
+    });
+    const parsed = parseSearchValue(get().search);
+    if (parsed.mode === "tag" && parsed.query === from) {
+      // An active tag-search points at the old name — repoint it so the gallery
+      // refreshes instead of showing stale results for a tag that no longer exists.
+      get().setSearch(`/t ${to}`);
+    } else if (get().activeView === "explore") {
+      await get().loadExploreTags();
+    }
+  },
+
+  deleteTag: async (tag) => {
+    const removed = await invoke<number>("delete_tag", { params: { tag } });
+    set({
+      exploreTagsFolderId: undefined,
+      exploreTagEntries: [],
+      tagCloudFolderId: undefined,
+      tagCloudEntries: [],
+    });
+    const parsed = parseSearchValue(get().search);
+    if (parsed.mode === "tag" && parsed.query === tag) {
+      // The searched tag is gone — reload so the now-empty result is reflected.
+      void get().loadImages(true);
+    } else if (get().activeView === "explore") {
+      await get().loadExploreTags();
+    }
+    return removed;
+  },
+
   // ── Gallery multi-select (Feature A) ──────────────────────────────────────
 
   toggleGallerySelected: (imageId) => {