feat(gitlab,bitbucket): warn when adding a repo already scoped on another connection

[mfrancisc]

Summary

Follow-up to #9034, which added the duplicate-scope warning for GitHub. This PR
extends the same feature to GitLab and Bitbucket, per the follow-up noted
in that PR's description (originally tracked in #8947).
When the same repository/project is added under more than one connection, DevLake
stores duplicate domain-layer records and metrics get inflated. The Config UI
previously allowed this with no warning for any plugin; #9034 fixed it for GitHub
only. This PR brings GitLab and Bitbucket to parity.
This PR adds:

• GET /plugins/gitlab/scope-duplicates and GET /plugins/bitbucket/scope-duplicates
  diagnostics (repos already on multiple connections) and a pre-add check
  (connectionId + gitlabIds/bitbucketIds)
• Generalization of the Config-UI data-scope-remote component and the scope API
  client so the same dismissible, non-blocking warning now renders for GitHub,
  GitLab, and Bitbucket alike, instead of being hardcoded to GitHub

Save is still allowed; users can choose to proceed intentionally, same as before.

Bitbucket-specific note

Unlike GitHub/GitLab (numeric scope IDs), Bitbucket identifies repositories with a
string owner/repo id. The new endpoint and query parsing handle this as a string
rather than assuming a numeric ID, including comma-separated bitbucketIds query
values (e.g. bitbucketIds=owner/repo-a,owner/repo-b).

Testing

• Added unit tests for both new endpoints' query parsing and row-grouping logic
  (scope_duplicates_api_test.go for each plugin), following the same test
  structure as the existing GitHub tests.
• Verified locally end-to-end via docker-compose-dev-mysql.yml: confirmed
  GET /plugins/{github,gitlab,bitbucket}/scope-duplicates all return 200 with
  the expected {"duplicates": [...]} shape, and that the Config UI bundle
  includes the generalized gitlabIds/bitbucketIds query-param logic.
• Manually tried to add the same repo to multiple connections, see :

Follow-ups

• global GET /api/scope-duplicates aggregator across all plugins