Add geocoding pipeline for Travis household coordinates

Problem

Sampled registered_voter.payload rows include residential address fields but no latitude/longitude. The current app falls back to deterministic Travis County placements from city/zip/household, which is good enough for UI wiring but not a real walking map.

Goal

Add a geocoding or address-coordinate import pipeline for Travis County household targets.

Suggested Approach

• Decide whether to use a public address point dataset, county GIS data, Mapbox geocoding, or another approved source.
• Normalize residential address + unit into a stable household key.
• Store lat/lng for each household target before Turf.js partitioning.
• Track geocoding confidence and failures.

Acceptance Criteria

• Household knock targets have real-world coordinates for the majority of Travis County rows.
• The dashboard and simulator use those coordinates.
• Failed/unmatched addresses are visible in verification output.
• No private API keys are committed.

Start by tracing how registered_voter.payload rows become household targets and where Turf.js partitioning, the dashboard, and simulator consume coordinates. Compare the approved geocoding or county-data options, then define the household key, confidence and failure output; done means most Travis County targets have real coordinates, consumers use them, failures are visible, and no private keys are committed.