fix: panic guards, dedup, and unsafe documentation

- diff.rs: graceful error instead of expect() on item ID in spawned thread
- common.rs: lazy_static regex, avoid unwrap on regex captures
- db.rs: ok_or_else guard on item.id in delete_item
- list/get/info/export/client/list: use settings.meta_filter() helper
- item_service.rs: expect() on meta lock instead of silent swallow
- filter_plugin/mod.rs: extract parse_encoding_option() helper
- main.rs: document unsafe libc::umask block with safety rationale

src/modes/list.rs

@@ -89,12 +89,7 @@ pub fn mode_list(
     data_path: std::path::PathBuf,
 ) -> Result<()> {
     let item_service = ItemService::new(data_path.clone());
-    let meta_filter: std::collections::HashMap<String, Option<String>> = settings
-        .meta
-        .iter()
-        .map(|(k, v)| (k.clone(), v.clone()))
-        .collect();
-    let items_with_meta = item_service.get_items(conn, ids, tags, &meta_filter)?;
+    let items_with_meta = item_service.get_items(conn, ids, tags, &settings.meta_filter())?;
 
     if settings.ids_only {
         for item_with_meta in &items_with_meta {