[Data Source] Build Kansas City Council Legistar meeting and vote scraper

[ThatXliner]

Goal

Add a current-cycle Kansas City Council scraper using the official Legistar portal and provider-neutral local-government contract from #181.

Official sources

• Calendar: https://clerk.kcmo.gov/Calendar.aspx
• Council body: https://clerk.kcmo.gov/DepartmentDetail.aspx?GUID=1B48510D-ACF9-410D-AB56-5B087BBBB437&ID=43595
• Legistar host: https://kansascity.legistar.com/
• City Clerk: https://www.kcmo.gov/city-hall/clerk

Scope

• Limit discovery to the Council primary legislative body and current council/election cycle; no historical backfill.
• Ingest meetings, cancellations/amendments, locations, agenda/packet/minutes documents, videos, items, legislation references, actions, outcomes, and named votes.
• Prefer structured Legistar endpoints and stable Event/Item/Vote IDs.
• Persist into the shared meeting/document/agenda-item/vote tables and serve cached rows through the existing API.

Acceptance criteria

• Fixtures/tests cover Central Time/DST, regular/special/cancelled meetings, revisions, document replacement, actions, and votes.
• Shared retry/backoff, conservative concurrency, hashes/versions, idempotent upserts, env contract, and docs.
• Scraper/API/DB checks pass. No credentials required.