feat: add Edit contact button to email viewer contact sidebar

Clicking an email address in the viewer already shows a contact detail
sidebar. An "Edit" button now appears there (for known contacts) that
navigates directly to the contact edit form via the existing URL-param
intent system (?contactId=…&view=edit), removing the need to open the
Contacts page manually and search for the contact.

locales/ja/common.json

@@ -544,7 +544,25 @@
     "reschedule_prompt": "新しい日時を入力してください。例: 2026-05-04T15:30",
     "scheduled_actions_only": "予約済みビューでは予約アクションのみ利用できます",
     "undo_send_scheduled": "メッセージは送信予約されています",
-    "undo_send": "送信を取り消す"
+    "undo_send": "送信を取り消す",
+    "contact_sidebar": {
+      "title": "Contact",
+      "close": "Close sidebar",
+      "action_email": "Email",
+      "action_email_title": "Send email",
+      "action_copy": "Copy",
+      "action_copy_title": "Copy email",
+      "action_edit_title": "Edit contact",
+      "section_emails": "Emails",
+      "section_phones": "Phones",
+      "section_organizations": "Organizations",
+      "section_addresses": "Addresses",
+      "section_notes": "Notes",
+      "not_in_contacts": "Not in your contacts",
+      "add_to_contacts": "Add to contacts",
+      "copied": "Copied!",
+      "copy_failed": "Failed to copy"
+    }
   },
   "email_composer": {
     "read_receipt_on": "開封確認を要求中（クリックで無効化）",