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/application/services/admin_settings_service.rs

@@ -139,11 +139,10 @@ impl AdminSettingsService {
         self.settings_repo.set("oidc.issuer_url", &dto.issuer_url, cat, false, by).await?;
         self.settings_repo.set("oidc.client_id", &dto.client_id, cat, false, by).await?;
 
-        if let Some(ref secret) = dto.client_secret {
-            if !secret.is_empty() {
+        if let Some(ref secret) = dto.client_secret
+            && !secret.is_empty() {
                 self.settings_repo.set("oidc.client_secret", secret, cat, true, by).await?;
             }
-        }
         if let Some(ref v) = dto.scopes {
             self.settings_repo.set("oidc.scopes", v, cat, false, by).await?;
         }