feat(taxonomy): add property events list on property detail

[lordspline]

Problem

Property detail pages did not show which event definitions currently use a property, forcing users to infer usage elsewhere or run heavier event queries. This fixes PostHog#26463 by exposing ingestion metadata on the property detail view without a live ClickHouse scan.

Changes

• Adds GET /api/projects/{project_id}/property_definitions/{id}/events/ with typed serializers, property_definition:read permissions, limit/offset pagination, and team-scoped Postgres metadata queries.
• Uses posthog_eventproperty as the authoritative association source populated asynchronously by ingestion; joins to current EventDefinition rows for navigation and event-level last-seen context, so deleted event definitions are omitted and empty means no current event definition is known to use the property.
• Adds a Data management property-detail section with loading, error/retry, empty, pagination, count, freshness copy, event last-seen context, and links to each event definition.
• Regenerates OpenAPI/frontend/MCP artifacts for the new typed endpoint; the MCP scaffolded tool remains disabled.
• Adds backend and frontend tests for scoping, permissions, pagination, stale/deleted definitions, empty state, query count, loader behavior, and UI rendering.

How did you test this code?

• Agent-run: hogli test posthog/api/test/test_property_definition.py -k property_definition_events — 7 passed.
• Agent-run: hogli test frontend/src/scenes/data-management/definition/definitionLogic.test.ts frontend/src/scenes/data-management/definition/DefinitionView.test.tsx — 9 passed.
• Agent-run: hogli build:openapi -y.
• Agent-run: pnpm --filter=@posthog/frontend typegen:check -- --files src/scenes/data-management/definition/definitionLogic.ts.
• Agent-run: pnpm --filter=@posthog/frontend typescript:check.
• Agent-run: pnpm --filter=@posthog/mcp typecheck.
• Agent-run: ruff format --check / ruff check on touched Python files and oxfmt --check / oxlint on touched frontend files.
• Agent-run browser verification against local PostHog: seeded one populated property and one empty property, verified populated count/list/last-seen/link navigation, and verified the empty state.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

Docs update

No docs update; this is an in-product Data management detail-page improvement.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Captain Capy implemented this end to end. The main design choice was to use ingestion-maintained posthog_eventproperty metadata joined with current EventDefinition rows, rather than scanning raw event data, because the product need is a current metadata association list with explicit asynchronous freshness semantics. The new endpoint is typed and generated for frontend use; the MCP YAML was synced but left disabled by default.

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