[Freshdesk] Surface "sync existing knowledge base" as its own section, not buried under "See all"

[mattsmith-fin]

Platform: Standalone for Fresh(desk/chat)
Type: Improvement (discoverability / UX)
Owning team: Knowledge

Context
When setting up Fin on Freshdesk, customers can sync their existing Freshdesk
knowledge-base articles as a content source for Fin. Today this is only reachable
inside the "See all" section, so customers setting Fin up for the first time don't
realise it exists.

Current behaviour

• Syncing existing Freshdesk KB pages is listed under "See all", alongside every
  other content source.
• It is not discoverable during first-time setup.

Expected behaviour

• "Sync your existing Freshdesk knowledge base" appears as its own dedicated
  section at the start of the content-source step, above "See all".
• It reads as a primary, recommended setup action.

Acceptance criteria

• A dedicated Freshdesk KB-sync section renders at the top of the content-sources step.
• Includes the historic conversation sync and live knowledgebase sync
• The capability is no longer reachable only via "See all".
• Copy makes clear these are the customer's existing Freshdesk KB pages.
• Remove the Zendesk logo on see all, use Fresh logos in new section