refactor: apply clippy auto-fixes (162 warnings resolved)

- Fix needless borrows and references
- Collapse nested if statements
- Replace manual strip_prefix with str::strip_prefix()
- Remove redundant closures in map/unwrap_or_else
- Use Iterator::next_back() instead of rev().next()
- Simplify map_or patterns
- Use std::io::Error::other() instead of new(ErrorKind::Other, ..)
- Use div_ceil() instead of manual ceiling division
- Consolidate format! string arguments
- Various other idiomatic Rust improvements

39 files changed, 220 insertions(+), 320 deletions(-)

src/infrastructure/services/write_behind_cache.rs

@@ -256,13 +256,12 @@ impl WriteBehindCache {
                         pending.get(&file_id).cloned()
                     };
                     
-                    if let Some(entry) = entry {
-                        if let Err(e) = self.flush_single(&file_id, &entry).await {
+                    if let Some(entry) = entry
+                        && let Err(e) = self.flush_single(&file_id, &entry).await {
                             tracing::error!("Failed to flush {}: {}", file_id, e);
                             // Keep in cache for retry
                             continue;
                         }
-                    }
                 }
                 FlushCommand::FlushAll => {
                     let entries: Vec<_> = {