feat(web): move feedback entry from floating button to about section (#112)

Replace the fixed bottom-right ember-500 floating button with a
dedicated fourth column in the about grid, matching existing visual
language (smallcaps heading + icon link). Adds submitFeedback and
feedbackDescription i18n keys for zh-CN, en, ja.

Grid uses md:grid-cols-2 lg:grid-cols-4 for better mid-screen
responsiveness.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

lib/i18n/locales/en.ts

@@ -120,6 +120,7 @@ export const en = {
       cancel: "Cancel",
       saveAndSelect: "Save and Select",
       feedback: "Feedback",
+      submitFeedback: "Submit Feedback",
     },
 
     styleModal: {
@@ -165,6 +166,7 @@ Dreamy watercolor style with soft tones and nostalgic atmosphere
       contact: "CONTACT",
       email: "Email",
       openSource: "OPEN SOURCE",
+      feedbackDescription: "Your thoughts matter — tell us about your experience and suggestions.",
       betaUsers: "BETA USERS",
       qqGroupLabel: "QQ Group: ",
       qqGroupAlt: "InfiPlot Public Beta Group QR Code (Group ID: 575404333)",