mosaic chain added

[BKTB888]

Adds Mosaic, a Polkadot parachain, to data/networks-polkadot.yaml, along with its chain and token logos.

Network details

id	mosaic
relay	Polkadot
token	MOS, 18 decimals
ss58 prefix	0
runtime	mosaic-chain v109
rpcs	6

Notes on the config

• isDefault: false
• No coingeckoId — MOS is not listed on CoinGecko yet.
• Six RPCs listed though the build keeps the top five by health; the sixth is a spare for when one goes unhealthy.
• Symbol, decimals, prefix, genesis hash and spec version are all left to the build to fetch from the chain, as usual.

Verification

• All six RPCs accept wss:// connections and answer system_chain with "Mosaic Chain". system_properties reports MOS / 18 / ss58 0 consistently across every node.
• validate-schema passes against DotNetworksConfigFileSchema.
• generate-schemas regenerates all four JSON schemas byte-identical — no schema drift.
• Ran getNetworkLogoUrl and getTokenLogoUrl against the new assets: both resolve, so the network and the MOS token each render a logo despite the missing coingeckoId.

Mosaic won't appear in pub/ until fetch-external has recorded RPC health and chain specs for the new id — expected on a first-time addition.