Add in-app micro-feedback prompts for new features

Show a one-time toast asking how a feature is working after its third
successful use, with an optional comment sent anonymously to the Yaak
API (feature key, text, app version, and OS only — nothing identifying,
and nothing is sent unless the user clicks Send).

- New cmd_send_feedback Tauri command posts fire-and-forget via the
  shared API client (localhost in dev)
- Feature keys registry (cookie-editor, response-history, sse-summary,
  git-sync) with per-feature use counting in the key-value store
- "Never ask for feedback" setting to disable prompts entirely
- Toast gains dynamicHeight and hideDismiss props for richer content
- Fix missing vertical padding on xs/2xs multiline inputs
- Fix unused-import and dead-code warnings in yaak-system-appearance
  on non-Linux builds

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates-tauri/yaak-app-client/src/feedback.rs

@@ -0,0 +1,47 @@
+use log::debug;
+use serde::Serialize;
+use tauri::{AppHandle, Runtime, is_dev};
+use yaak_api::{ApiClientKind, yaak_api_client};
+use yaak_common::platform::get_os_str;
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct FeedbackPayload {
+    feature: String,
+    text: String,
+    app_version: String,
+    os: String,
+}
+
+/// Send explicit user feedback for a feature. Fire-and-forget: errors are
+/// logged and swallowed so a failed send never surfaces to the user.
+pub async fn send_feedback<R: Runtime>(app_handle: &AppHandle<R>, feature: String, text: String) {
+    let app_version = app_handle.package_info().version.to_string();
+    let payload = FeedbackPayload {
+        feature,
+        text,
+        app_version: app_version.clone(),
+        os: get_os_str().to_string(),
+    };
+
+    let client = match yaak_api_client(ApiClientKind::App, &app_version) {
+        Ok(c) => c,
+        Err(e) => {
+            debug!("Failed to build feedback client: {e:?}");
+            return;
+        }
+    };
+
+    match client.post(build_url("/app-feedback")).json(&payload).send().await {
+        Ok(resp) => debug!("Sent feedback with status {}", resp.status()),
+        Err(e) => debug!("Failed to send feedback: {e:?}"),
+    }
+}
+
+fn build_url(path: &str) -> String {
+    if is_dev() {
+        format!("http://localhost:9444/api/v1{path}")
+    } else {
+        format!("https://api.yaak.app/api/v1{path}")
+    }
+}

crates-tauri/yaak-app-client/src/lib.rs

@@ -65,6 +65,7 @@ use yaak_tls::find_client_certificate;
 mod commands;
 mod encoding;
 mod error;
+mod feedback;
 mod git_ext;
 mod git_watcher;
 mod grpc;
@@ -292,6 +293,16 @@ async fn cmd_render_template<R: Runtime>(
     Ok(result)
 }
 
+#[tauri::command]
+async fn cmd_send_feedback<R: Runtime>(
+    app_handle: AppHandle<R>,
+    feature: String,
+    text: String,
+) -> YaakResult<()> {
+    feedback::send_feedback(&app_handle, feature, text).await;
+    Ok(())
+}
+
 #[tauri::command]
 async fn cmd_dismiss_notification<R: Runtime>(
     window: WebviewWindow<R>,
@@ -1819,6 +1830,7 @@ pub fn run() {
             cmd_delete_send_history,
             cmd_dismiss_notification,
             cmd_export_data,
+            cmd_send_feedback,
             cmd_http_request_body,
             cmd_http_response_body,
             cmd_format_json,