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/common/stubs.rs

@@ -621,7 +621,11 @@ pub struct StubSearchUseCase;
 
 #[async_trait]
 impl SearchUseCase for StubSearchUseCase {
-    async fn search(&self, _criteria: SearchCriteriaDto, _user_id: &str) -> Result<SearchResultsDto, DomainError> {
+    async fn search(
+        &self,
+        _criteria: SearchCriteriaDto,
+        _user_id: &str,
+    ) -> Result<SearchResultsDto, DomainError> {
         Ok(SearchResultsDto::empty())
     }
 
@@ -794,7 +798,14 @@ impl ContentCachePort for StubContentCachePort {
         None
     }
 
-    async fn put(&self, _file_id: String, _content: Bytes, _etag: Arc<str>, _content_type: Arc<str>) {}
+    async fn put(
+        &self,
+        _file_id: String,
+        _content: Bytes,
+        _etag: Arc<str>,
+        _content_type: Arc<str>,
+    ) {
+    }
 
     async fn invalidate(&self, _file_id: &str) {}