refactor: decouple provider linking from Unrecognized Files, add FileSearch entry point

[harshithmohan]

Summary

In preparation for adding edit release info functionality, this moves the Link With Providers page from a child route of Unrecognized Files to a standalone top-level utility, accessible from both Unrecognized Files and File Search (new "Edit Link" button). For already-linked files, fetches existing ReleaseInfo via GET ReleaseInfo/File/{fileID} instead of forcing AutoPreview.

Key changes

• Standalone route: /webui/utilities/link-with-providers (was /webui/utilities/unrecognized/files/link-with-providers)
• FileSearch entry point: new "Edit Link" button passes selectedRows via router state, same as Unrecognized Files
• Already-linked files: detects file.Imported → state: "fetching" → GET ReleaseInfo/File/{id} → ready for re-submission
• LinkState enum → LinkStateType string union with additional "fetching" state
• useLinkWorkflow hook: extracts state machine (process handlers, drive loop, guard sets) from component
• releaseInfoHelpers.ts: extracts createLinksFromFiles and mergeReleaseInfo pure helpers
• State-group constants: BUSY_STATES, NOT_SELECTABLE_STATES, EDITABLE_STATES as Sets
• Rename UnrecognizedVideo → LinkCard: component is no longer Unrecognized-specific