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/infrastructure/services/password_hasher.rs

@@ -39,13 +39,12 @@ impl Argon2PasswordHasher {
     ///
     /// Panics at startup if the parameters are invalid (caught immediately).
     pub fn new(memory_cost: u32, time_cost: u32, parallelism: u32) -> Self {
-        let params = Params::new(memory_cost, time_cost, parallelism, None)
-            .unwrap_or_else(|e| {
-                panic!(
-                    "Invalid Argon2 parameters (m={}, t={}, p={}): {}",
-                    memory_cost, time_cost, parallelism, e
-                )
-            });
+        let params = Params::new(memory_cost, time_cost, parallelism, None).unwrap_or_else(|e| {
+            panic!(
+                "Invalid Argon2 parameters (m={}, t={}, p={}): {}",
+                memory_cost, time_cost, parallelism, e
+            )
+        });
 
         tracing::info!(
             "Argon2PasswordHasher initialized: m_cost={} KiB, t_cost={}, p_cost={}",