feat: add cache toggle, unregister API and chunk training docs

- Add POST /api/v1/config/cache for cache toggle
- Add POST /api/v1/unregister for video deletion
- Add CHUNK_DATA_STRUCTURE.md for marcom training
- Fix processor_results query in delete_video

src/core/db/postgres_db.rs

@@ -584,6 +584,40 @@ impl PostgresDb {
         Ok(())
     }
 
+    pub async fn delete_video(&self, uuid: &str) -> Result<()> {
+        tracing::info!("[PostgresDb] Deleting video: {}", uuid);
+
+        let tx = self.pool.begin().await?;
+
+        sqlx::query("DELETE FROM chunk_vectors WHERE uuid = $1")
+            .bind(uuid)
+            .execute(&self.pool)
+            .await?;
+
+        sqlx::query("DELETE FROM chunks WHERE uuid = $1")
+            .bind(uuid)
+            .execute(&self.pool)
+            .await?;
+
+        sqlx::query("DELETE FROM processor_results WHERE video_id IN (SELECT id FROM videos WHERE uuid = $1)")
+            .bind(uuid)
+            .execute(&self.pool)
+            .await?;
+
+        sqlx::query("DELETE FROM videos WHERE uuid = $1")
+            .bind(uuid)
+            .execute(&self.pool)
+            .await?;
+
+        tx.commit().await?;
+
+        let mut cache = self.cache.write().await;
+        cache.videos.remove(uuid);
+
+        tracing::info!("[PostgresDb] Video deleted: {}", uuid);
+        Ok(())
+    }
+
     pub async fn get_storage_status(&self, uuid: &str) -> Result<Option<StorageStatus>> {
         if let Some(video) = self.get_video_by_uuid(uuid).await? {
             Ok(Some(video.storage))