chore(lint): clean up clippy warnings across workspace

Auto-applied cargo clippy --fix across 11 files — needless return,
unnecessary cast, map_or simplification, repeat().take() → repeat_n(),
iter().any() → contains(), manual char comparison, lifetime elision,
push_str single-char, reference immediately dereferenced.

Also fixed three lints on file_storage.rs manually: two doc-list-item
overindentations, plus the same needless-return. Baseline main was
not clippy-clean with -D warnings before; after this pass one
needless_range_loop warning remains (live.rs:1089) that clippy's
suggested rewrite would make less readable — left for a dedicated
refactor session.

Build + workspace tests remain green (245 passing, 0 failing, 1
ignored).

src-tauri/build.rs

@@ -64,7 +64,7 @@ fn assert_localhost_llm_csp() {
     let tokens: Vec<&str> = connect_src.split_whitespace().collect();
     for required in ["http://127.0.0.1:*", "ws://127.0.0.1:*"] {
         assert!(
-            tokens.iter().any(|t| *t == required),
+            tokens.contains(&required),
             "build.rs: tauri.conf.json CSP connect-src must permit {required} \
              for local LLM connectivity (brief item #2). Current connect-src: \
              {connect_src:?}"