fix(dashboard, api): Add stronger validation for frontend and backend workflow schemas

[rifont]

What changed? Why was the change needed?

• Enforce minimum and maximum name length
• Enforce maximum description length
• Enforce maximum tags count
• Enforce maximum tags.{number} length

Screenshots

Name required

Maximum name length exceeded

Maximum tag count exceeded

Maximum tag length exceeded

Textarea counter

Expand for optional sections

### Related enterprise PR ### Special notes for your reviewer

[linear[bot]]

NV-4793 Unify frontend and backend validations

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[rifont]

@rifont how does zod and class validation work in the new approach? Do we replicate the validation logic in both or do they complement each other?

They are replicated in both Zod + Class validators currently. This PR adds the minimum necessary BE validation for now. We need to narrow down the strategy for shared validation between the FE/BE, we'll continue that in a follow-up PR.