fix: resolve all clippy warnings and enforce cargo fmt

- display_helpers: convert module doc-comments to regular comments,
  merge identical text/markdown + text/ branches
- search_service: replace needless range loops with slice-based pagination
- folder_repository, folder_db_repository: collapse nested if statements
- favorites_pg_repository: remove unnecessary borrow on generic arg
- file_blob_read_repository: collapse 6 nested if-let blocks
- file_blob_write_repository: collapse nested if for dedup ref decrement
- chunked_upload_service: use div_ceil(), collapse 2 nested if blocks
- folder_handler: collapse nested if-let for owner check
- webdav_handler: replace 7x io::Error::new(ErrorKind::Other, ..) with
  io::Error::other(..)
- cargo fmt applied to all files

Passes: cargo clippy --all-targets --all-features -- -D warnings

src/application/services/batch_operations.rs

@@ -713,7 +713,10 @@ impl BatchOperationService {
                             match chunk {
                                 Ok(bytes) => {
                                     if let Err(e) = zip.write_all(&bytes) {
-                                        info!("Could not write zip chunk for {}: {}", file_dto.name, e);
+                                        info!(
+                                            "Could not write zip chunk for {}: {}",
+                                            file_dto.name, e
+                                        );
                                         break;
                                     }
                                 }