Auto-fix JSON comments and trailing commas for HTTP request bodies

Add a per-request "Automatically Fix JSON" toggle (default: on) that strips
comments and trailing commas before sending HTTP requests. When disabled,
comments are sent as-is and the editor linter flags them as errors.

- New JsonBodyEditor component with settings dropdown and dismissible banner
- Configurable JSON linter (allowComments/allowTrailingCommas) via lintExtension prop
- strip_trailing_commas pass in Rust strip_json_comments pipeline
- Fix JSON formatter pulling standalone comments onto previous comma line
- Add get_bool_map helper, maybe_strip_json_comments, and related tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/yaak-common/src/serde.rs

@@ -21,3 +21,10 @@ pub fn get_str_map<'a>(v: &'a BTreeMap<String, Value>, key: &str) -> &'a str {
         Some(v) => v.as_str().unwrap_or_default(),
     }
 }
+
+pub fn get_bool_map(v: &BTreeMap<String, Value>, key: &str, fallback: bool) -> bool {
+    match v.get(key) {
+        None => fallback,
+        Some(v) => v.as_bool().unwrap_or(fallback),
+    }
+}