Expand interactive card payload schemas in uagents-core

[tejus3131]

Prerequisites

• I checked the documentation and made sure this feature does not already exist
• I checked the existing issues to make sure this feature has not already been requested

Feature

Extend uagents_core.contrib.protocols.chat.cards so Python card payload validation matches the Agentverse interactive card spec (predefined cards + custom element-tree primitives).

#897 added basic interactive cards; current schemas are missing fields and validation that Agentverse drawer already supports.

Scope:

• Predefined cards: carousel (style, root_cta, logo, DisplayImage images), detail (ExpandedChoice, hero media), form (cancel_cta, full input kinds), review (stricter CtaAction)
• Shared: DisplayImage, HTTP URL + aspect_ratio validation, non-empty CTA selections
• Custom element tree: VideoNode, LabelWithIcon button labels, button image/redirect/bypass_required_validation, InputNode parity with form fields (date/time/multiselect/phone), ChoiceGrid DisplayImage support, group gap >= 1

Outcome: agents using uagents-core emit/validate the same card payloads Agentverse clients render. Metadata wire format stays v1; no protocol digest change.

Additional Information (Optional)

Follow-up to #897.

Implementation: expand Pydantic models + validators in python/uagents-core/uagents_core/contrib/protocols/chat/cards/__init__.py.

Non-breaking for valid #897 payloads. Tighter validation may reject previously loose/invalid payloads (empty CTA selections, bad URLs, etc.) — intentional per spec.