Bitbucket connector

[kiranfin]

Related issue

Closes #287

Short summary

Adds the Bitbucket Cloud repository connector to the frontend so Bitbucket repositories can be discovered, connected, synced and browsed in the same way as GitHub repositories, across data ingestion, the create-project wizard, the knowledge base, the connector overview and the chat filter.

• Service layer: new bitbucketService for the backend Bitbucket endpoints (connectBitbucketRepository / connectBitbucketRepositories via POST /api/v1/bitbucket and /connect/all, discoverBitbucketRepositories via GET /api/v1/bitbucket/discover/workspace/{workspace} with paging and hasMore, addBitbucketRepositoryToProject / removeBitbucketRepositoryFromProject, updateBitbucketRepository, updateAllBitbucketRepositories, getBitbucketRepositoryConfig / configureBitbucketRepository / configureAllBitbucketRepositories). The discover DTO is mapped defensively. bitbucketRepositoryInput parses workspace and workspace/slug input as well as bitbucket.org URLs. BITBUCKET is added to the source type unions, together with a BitbucketIcon and a wider IconComponent type so SOURCE_META, DrawerCard and ConnectorMeta accept non-lucide icons.
• Data ingestion page: Bitbucket source cards are built from the per-repo status row alone (createBitbucketSourceFromInstance, BitbucketRepositoryDetails), show the workspace, and the run history filters by repositoryId with workspace/slug run labels. The source drawer gets a Bitbucket repository card with enable toggle (patchConnectorSources("bitbucket")), manual update, remove from project and a per-repo sync schedule. The global sync settings modal gets a Bitbucket tab.
• Provider-neutral repository discovery: search, paging, multi-select and link-state handling moved out of GithubRepositoryDiscovery into a new RepositoryDiscovery driven by an adapter and a credential picker slot. GithubRepositoryDiscovery is now a thin wrapper with unchanged props. The already-ingested and in-project lookups filter by source system, so a Bitbucket repo never shows up as a linkable GitHub repo.
• Add-source flow: new BitbucketRepositoryDiscovery with an Atlassian credential picker and a BitbucketDraftSource that either links an already-ingested repo or connects a new one. Wired into AddSourceFlow and AddSourceModal, Bitbucket drafts appear in the staged list and the review step.
• Create-project wizard: CreateProjectWizard offers Bitbucket as a source type, stages Bitbucket drafts from the discovery selection and automatically selects a newly added inline Atlassian credential. Works alone and mixed with GitHub.
• Knowledge base, connectors and chat: parseBitbucketMetadata makes the repository badge, repository facet and URL state work for Bitbucket as well as GitHub. Adds an "Open in Bitbucket" link badge and icon, reads /pull-requests/ links as pull requests and adds CONNECTOR_META.bitbucket. ChatPage maps bitbucket.org citations to BITBUCKET, and BITBUCKET is added to the chat SOURCE_SYSTEMS filter.
• Smaller fixes: shows a helpful message instead of a bare 500 when connecting fails. Updates the Atlassian credential copy to mention Bitbucket next to Jira and Confluence.
• Covered by unit + a11y tests (bitbucketService, bitbucketRepositoryInput, RepositoryDiscovery, BitbucketRepositoryDiscovery a11y, AddSourceModal, CreateProjectWizard + a11y, projectSourcesDraft, SourceDetailsPanel + a11y, SourceList, RunDetailsPanel, DataIngestionPage, data, githubMetadata, ArtifactFilters, ArtifactViewerDrawer, SourceLinkBadge, useKnowledgeBase, useKnowledgeBaseUrlState, connectorMeta, useAvailableSources) plus new MSW handlers for the Bitbucket endpoints.

Checks

• I verified the code makes sense intuitively
• The PR changes affect only this issue, no unrelated/unwanted code changes to other modules/code segments
• CI runs (npm ci, npm run lint, npm run build)
• New logic is unit tested (Vitest), including a11y tests for changed pages/components
• The new functionality is tested manually

Additional notes

⚠️ Backend dependency: Merge the Bitbucket connector backend first Bitbucket Repository Connector Backend

• requires the /api/v1/bitbucket/... endpoints (connect, discover, project link, update, config)
• requires BITBUCKET in the per-repo ingestion status and run history

⚠️ Backend follow-up: Bitbucket connector fixes SprintStartProject/sprintstart-backend#271

• allows BITBUCKET in the source_system DB check constraints (otherwise ingestion fails)
• lists Bitbucket repositories in the knowledge base repository facet
• returns 404 instead of 500 for a missing Bitbucket repository, and fixes the pull request sync and manual updates

⚠️ AI dependency: the chat source filter needs the AI change SprintStartProject/sprintstart-ai#214

• BITBUCKET in the chat SOURCE_SYSTEMS is only accepted once the AI service knows the value, otherwise filtering by Bitbucket returns a 422