feat(data-management): add property usage events list

[lordspline]

Problem

When viewing an event property definition in Data management, users cannot see which events use that property. This makes it difficult to understand property usage and impact without manual queries or workarounds.

Changes

• /api/projects/{id}/property_definitions/{id}/events/ endpoint lists events that have used a property, with event definition IDs and last seen timestamps
• Added typed serializers and full-stack tests
• Added “Events using this property” table section to the property definition page, linking to event definitions
• Enhanced demo data generators to seed EventProperty relationships for realistic testing

How did you test this code?

• Backend: regression tests in test_list_events_using_property and test_list_events_using_property_is_project_scoped
• Frontend: updated definitionLogic.test.ts to assert property usage events loading
• Browser: manually verified on the plan property page showing entered_free_trial, pageview, and purchase events

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[capy-ai]

Added 1 comment

[capy-ai]

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[capy-ai]

Added 1 comment

[capy-ai]

🖼 Visual QA — property definition page

Surface: Data management → Properties → {property definition}
Tested on: $browser property with demo data (Hedgebox workspace, 7 events)

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Before — master (desktop 1280px)

The property definition page ends after Verification Status / Property Type. No events section.

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After — PR (desktop 1280px)

New "Events using this property" section appears below, with a paginated table.

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After — PR (narrow 390px)

Table remains readable at mobile width; EVENT name + internal key stack vertically per row.

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✅ Checks

New section renders for property definitions	✅
Section absent on master	✅
Display name + internal key shown per event row	✅
Event name links to event definition	✅
Relative "last seen" timestamps render correctly	✅
Null last_seen_at renders as —	✅
Section description text matches spec	✅
Responsive at 390px — no overflow	✅

⚠️ Minor observation

uploaded_file showed — for last seen at desktop width in one screenshot but a timestamp in narrow — likely a data race between the two captures (demo data was still being generated). Not a rendering bug; worth a quick manual sanity check.