docs(swagger): expose launchpad dev buy fields

[joshuakrueger-dfx]

Summary

Documents the launchpad dev buy fields in the API swagger schema so consumers see the seeded creator buy on launchpad token and activity responses.

Changes

• src/swagger/schemas.ts — dev buy fields on the relevant launchpad schemas.

Part of the dev buy stack

• bapp — dev buy at token creation (atomic, Permit2): feat(launchpad): dev buy at token creation bapp#772
• ponder — indexes dev buys: feat(launchpad): index dev buys ponder#140

[Danswar]

Dev buy stack — linking the related PRs:

• Swagger docs (this PR): docs(swagger): expose launchpad dev buy fields #268
• Frontend: feat(launchpad): dev buy at token creation bapp#772
• Indexer: feat(launchpad): index dev buys ponder#140

This PR is just swagger docs, so it's harmless to merge on its own — but heads up that the fields it documents aren't produced yet. The whole stack depends on a TokenFactory with createTokenWithDevBuyPermit / DevBuyExecuted, which doesn't exist in JuiceSwapxyz/launchpad (any branch), isn't in the published package, and isn't deployed (verified the live mainnet factory bytecode — neither the function selector nor the event topic is present).

So these docs describe future behavior until the contract ships. Critical path: contract → ponder#140 → api#268 → bapp#772.