F7: Flock management — edit/deplete/archive + Flocks screen #47

Part of Phase 1.1 (epic #14). Flocks today: API create/list/get/deplete, SPA has only inline create on Daily entry — no screen, no edit, no deplete UI, Archived status unreachable.

Scope

Domain

• Flock.Update(name, breed, placementDate, initialCount) — fix typos/corrections. Guards mirror Create.
• Flock.Archive() — allowed from Active or Depleted (mistake-created flocks can be archived directly). Deplete() stays Active-only.
• Version concurrency token on Flock — Update/Deplete/Archive all bump it (AGENTS.md rule; Deplete currently has no token at all). Migration adds the column.

API

• PUT /flocks/{id} — update.
• POST /flocks/{id}/archive.
• GET /flocks gains includeArchived (default false): archived flocks disappear from pickers/dashboard; Depleted stay visible (recent-history value). Management view passes true.

Web

• New "Flocks" screen: table (name, breed, placed, age in weeks, initial count, status), create form, inline edit, deplete/archive actions with status-appropriate buttons, archived toggle. Scoped idempotency keys per established contract.
• Daily entry keeps its inline quick-create.

Out of scope

• Current bird count math (initial − mortality − culls) — that's the mortality/bird-movement slice; this screen shows initial count only.

Acceptance

• Full loop from SPA: create → edit → deplete → archive; archived flock leaves daily-entry flock picker and dashboard, still listed on Flocks screen with toggle.
• Double-deplete / archive-of-archived → 409.
• Parallel-update race test: no torn write, Version advances per success.