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/image_transcode_service.rs

@@ -200,11 +200,7 @@ impl ImageTranscodeService {
         // Calculate savings
         let original_size = original_content.len();
         let transcoded_size = transcoded_bytes.len();
-        let saved = if transcoded_size < original_size {
-            original_size - transcoded_size
-        } else {
-            0
-        };
+        let saved = original_size.saturating_sub(transcoded_size);
         
         // Only use transcoded if it's actually smaller
         if transcoded_size >= original_size {