feat(FR-2382): add Model Store improvement feature spec

[yomybaby]

Resolves #FR-2382

Summary

• Add feature specification for Model Store improvement (Epic FR-1927)
• Covers four key areas:
  • Admin one-step HuggingFace model import flow
  • Storage-based model item filtering for users
  • Model item list UI redesign (thumbnail cards → clean list)
  • End-to-end clone-to-service launch flow improvement

Test plan

• Spec file renders correctly in GitHub
• Acceptance criteria are verifiable
• All user stories cover admin and user perspectives

[yomybaby]

• feat(FR-2382): add Model Store improvement feature spec #6173 👈 (View in Graphite)
• main

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