feat: Enhance Linear integration UX with multi-issue support and improved placement (#11668)

Fixes
https://linear.app/chatwoot/issue/CW-4150/support-for-multiple-issues-linking-in-linear

This PR significantly improves the Linear integration user experience by
relocating the Linear integration from the conversation header to the
contact panel and adding support for multiple issue linking per
conversation.

  ### Key Changes

- **Relocated Linear integration**: Moved from conversation header to
contact panel for better organization and accessibility
- **Multi-issue support**: Added ability to link/create multiple Linear
issues for a single conversation
- **Integration CTA**: Added a dedicated call-to-action section for
users who haven't connected their Linear account yet
  - **UI/UX improvements**: Enhanced design consistency and user flow




<details>
<summary>Screenshots</summary>

  #### Multiple Issues Support


![link-multiple-issues](https://github.com/user-attachments/assets/b56cfa7d-6f98-42db-b4bb-361ae59d0eae)

  #### Integration CTA


![link-multiple-issues](https://github.com/user-attachments/assets/a895fcbe-780a-47f8-9fa4-3a2af8b243e1)

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Pranav <pranavrajs@gmail.com>

app/javascript/dashboard/i18n/locale/en/conversation.json

@@ -308,6 +308,7 @@
       "CONTACT_ATTRIBUTES": "Contact Attributes",
       "PREVIOUS_CONVERSATION": "Previous Conversations",
       "MACROS": "Macros",
+      "LINEAR_ISSUES": "Linked Linear Issues",
       "SHOPIFY_ORDERS": "Shopify Orders"
     },
     "SHOPIFY": {

app/javascript/dashboard/i18n/locale/en/integrations.json

@@ -315,11 +315,18 @@
         "SUCCESS": "Issue unlinked successfully",
         "ERROR": "There was an error unlinking the issue, please try again"
       },
+      "NO_LINKED_ISSUES": "No linked issues found",
       "DELETE": {
         "TITLE": "Are you sure you want to delete the integration?",
         "MESSAGE": "Are you sure you want to delete the integration?",
         "CONFIRM": "Yes, delete",
         "CANCEL": "Cancel"
+      },
+      "CTA": {
+        "TITLE": "Connect to Linear",
+        "AGENT_DESCRIPTION": "Linear workspace is not connected. Request your administrator to connect a workspace to use this integration.",
+        "DESCRIPTION": "Linear workspace is not connected. Click the button below to connect your workspace to use this integration.",
+        "BUTTON_TEXT": "Connect Linear workspace"
       }
     }
   },