Fix dataset identity metadata

[karelxfi]

What changed

• group related datasets under the reviewed chain ecosystem used by sqd.dev
• add missing logos for all active datasets while preserving existing CDN-hosted assets
• vendor six brand assets under src/img/networks
• correct reviewed display names and missing testnet classifications
• add missing metadata for Robinhood Chain Mainnet and Testnet, TRON, and Ethereum Mainnet Trace Blocks

Why

The extended metadata still grouped several networks by dataset slug, while the website had already reviewed the correct chain families. Some active datasets also had no metadata or logo. That forced every downstream consumer to repeat the same overrides.

Validation

• parsed 215 records in src/sqd-network/mainnet/metadata.yml with PyYAML
• confirmed all 200 datasets in the live public Portal catalog have metadata
• confirmed Robinhood uses the canonical dataset IDs and chain IDs 4663 and 46630
• confirmed every metadata logo uses cdn.subsquid.io and resolves to a tracked file under src/img/networks
• inspected the newly vendored images
• ran git diff --check