feat(captain): Add paywall and expose Custom Tools (#13977)

# Pull Request Template

## Description

Custom tools is now discoverable on all plans

## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

Before:
<img width="390" height="446" alt="CleanShot 2026-04-02 at 13 40 11@2x"
src="https://github.com/user-attachments/assets/0a751954-f3ad-47d6-85b8-1e2f1476a646"
/>


After:

<img width="392" height="522" alt="CleanShot 2026-04-02 at 13 40 47@2x"
src="https://github.com/user-attachments/assets/62a252f6-2551-47a9-b50c-be949f08c456"
/>

<img width="1826" height="638" alt="CleanShot 2026-04-02 at 13 37 39@2x"
src="https://github.com/user-attachments/assets/77dc2a75-3d76-44cf-8579-8d3457879bd0"
/>


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

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

@@ -838,6 +838,18 @@
         "SUCCESS_MESSAGE": "Custom tool deleted successfully",
         "ERROR_MESSAGE": "Failed to delete custom tool"
       },
+      "PAYWALL": {
+        "TITLE": "Upgrade to use tools with Captain",
+        "AVAILABLE_ON": "Captain Tools are only available in Business and Enterprise plans. Please upgrade to Business plan to use the feature.",
+        "UPGRADE_PROMPT": "",
+        "UPGRADE_NOW": "Open billing",
+        "CANCEL_ANYTIME": ""
+      },
+      "ENTERPRISE_PAYWALL": {
+        "AVAILABLE_ON": "Captain Tools are only available in the paid plans.",
+        "UPGRADE_PROMPT": "Please upgrade to a paid plan to use this feature.",
+        "ASK_ADMIN": "Please reach out to your administrator for the upgrade."
+      },
       "TEST": {
         "BUTTON": "Test connection",
         "SUCCESS": "Endpoint returned HTTP {status}",