**Refactor directory scanning and add scan task support**

- Added a new `scan_directory` task to enable folder scans as asynchronous tasks while maintaining compatibility with the immediate backend.
- Introduced the `reconcile` function, replacing `generate_directory` for improved separation of concerns between database writes and read operations.
- Established a unique constraint on `Directory` (`one_directory_name_per_parent`) to prevent duplicate directories under the same parent.
- Added a "Scan" button to the frontend for re-reading folders from disk, along with new task invocation endpoints in the API.
- Updated tests across modules to validate the new `scan_directory` task, unique constraints, and database indexing logic.
- Improved cleanup logic for stale files, directories, and thumbnails to handle concurrent operations efficiently.
- Simplified `scan_comics` management command by removing user dependency and aligning it with the new `reconcile` function.
- Enhanced frontend components (`TheComicReader`, `TheComicList`, and others) to include lifecycle method cleanups, prevent memory leaks, and handle task-based scans.

frontend/src/components/TheComicReader.vue

@@ -131,10 +131,11 @@ export default {
       }).then(() => {
         this.deck.slide(this.current_page)
         api.put(set_read_url, {page: this.current_page})
-        this.deck.on( 'slidechanged', (event) => {
+        this.slideChanged = (event) => {
           this.$refs.comic_box.scrollIntoView({behavior: 'smooth'})
           api.put(set_read_url, {page: event.indexh})
-        });
+        }
+        this.deck.on('slidechanged', this.slideChanged);
       })
 
       this.hammertime = new Hammer(this.$refs.comic_box, {})
@@ -153,6 +154,17 @@ export default {
   },
   beforeUnmount() {
     window.removeEventListener('keyup', this.keyPressDebounce)
+    clearTimeout(this.key_timeout)
+    if (this.deck) {
+      if (this.slideChanged) {
+        this.deck.off('slidechanged', this.slideChanged)
+      }
+      try {
+        this.deck.destroy()
+      } catch (e) {
+        console.log(e)
+      }
+    }
     try {
       this.hammertime.off('swipeleft')
       this.hammertime.off('swiperight')