[Feature] Add setting for Enter/Ctrl+Enter to send messages (#550)

* i18n: add translations for send shortcut setting

* feat: configurable keyboard shortcut for sending messages

* refactor,review: using storage key for send shortcut

* Increase the width of the trigger in the settings dialog. Previously, at 160px, it hide the letter “d” from the word “Send.”

* Update components/chat-input.tsx

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* fix: from review, ctrl send support for mac

* refactor: from review, reduce local storage read

* fix: make send shortcut setting reactive without page refresh

---------

Co-authored-by: Biki Kalita <86558912+Biki-dev@users.noreply.github.com>
Co-authored-by: Dayuan Jiang <34411969+DayuanJiang@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>

lib/i18n/dictionaries/en.json

@@ -104,6 +104,10 @@
         "closeProtectionDescription": "Show confirmation when leaving the page.",
         "diagramStyle": "Diagram Style",
         "diagramStyleDescription": "Toggle between minimal and styled diagram output.",
+        "sendShortcut": "Send Shortcut",
+        "sendShortcutDescription": "Choose how to send messages.",
+        "enterToSend": "Enter to send",
+        "ctrlEnterToSend": "Cmd/Ctrl+Enter to send",
         "diagramActions": "Diagram Actions",
         "diagramActionsDescription": "Manage diagram history and exports",
         "history": "History",