Add notification system with admin UI and backend

Introduces a full notification system with support for Discord and Pushover backends, event triggers, and message formatting. Adds backend services, processors, and API endpoints for managing notifications, as well as a new Notifications tab in the admin settings UI. Updates documentation, database schema, and tests to cover notification features and approval workflow improvements. Also changes project license from MIT to AGPL v3.

src/lib/utils/path-mapper.ts

@@ -67,6 +67,66 @@ export class PathMapper {
     return transformedPath;
   }
 
+  /**
+   * Reverse transforms a local path to qBittorrent remote path (local-to-remote mapping)
+   *
+   * Example:
+   *   Local path: /downloads/Audiobook.Name
+   *   Config: { enabled: true, remotePath: 'F:\\Docker\\downloads\\completed\\books', localPath: '/downloads' }
+   *   Returns: F:\Docker\downloads\completed\books\Audiobook.Name
+   *
+   * @param localPath - Path from ReadMeABook's perspective (inside Docker)
+   * @param config - Path mapping configuration
+   * @returns Transformed path for qBittorrent (or original if mapping disabled/no match)
+   */
+  static reverseTransform(localPath: string, config: PathMappingConfig): string {
+    // 1. If mapping disabled, return original
+    if (!config.enabled) {
+      return localPath;
+    }
+
+    // 2. Handle empty paths
+    if (!localPath || !config.remotePath || !config.localPath) {
+      logger.warn('Empty path or config, returning original');
+      return localPath;
+    }
+
+    // 3. Normalize paths
+    const normalizedRemote = this.normalizePath(config.remotePath);
+    const normalizedLocal = this.normalizePath(config.localPath);
+    const normalizedLocalPath = this.normalizePath(localPath);
+
+    // 4. Check if local path starts with local prefix
+    if (!normalizedLocalPath.startsWith(normalizedLocal)) {
+      logger.warn(
+        `Path "${localPath}" does not start with local path "${config.localPath}". ` +
+        `Returning original path unchanged.`
+      );
+      return localPath;
+    }
+
+    // 5. Replace local prefix with remote prefix
+    const relativePath = normalizedLocalPath.substring(normalizedLocal.length);
+
+    // For remote path, preserve original path separators (important for Windows)
+    // Use the original remote path's separators instead of normalizing
+    const remoteSeparator = config.remotePath.includes('\\') ? '\\' : '/';
+    const remotePathNormalized = config.remotePath.replace(/[/\\]+$/, ''); // Remove trailing slashes
+
+    // Build the final path with remote separators
+    let transformedPath: string;
+    if (relativePath) {
+      // Convert forward slashes to remote separator
+      const relativeWithRemoteSep = relativePath.replace(/^[/\\]+/, '').replace(/\//g, remoteSeparator);
+      transformedPath = remotePathNormalized + remoteSeparator + relativeWithRemoteSep;
+    } else {
+      transformedPath = remotePathNormalized;
+    }
+
+    logger.info(`Reverse transformed "${localPath}" to "${transformedPath}"`);
+    return transformedPath;
+  }
+
   /**
    * Validates path mapping configuration
    *