PolkaVM Preparation: Integration research

[kylymo]

Original: Integration research of PolkaVM and compatibility with current infrastructure stack

Expanded description:
Prototype node/client connectivity, SDK usage, indexing approach, and signing/tx flow.

Acceptance criteria:

• Spike repo with PoC code
• Decision log on SDK/indexer choices

Tasks:

• Node/endpoint evaluation
• SDK/API experiments
• Indexing strategy spike