Add saved home address routing

[cafca]

Summary

• add per-user named location storage with home location API
• add home address save/reset controls and start-at-home routing behavior
• render a home pin and fix dev tile proxy target for Docker hot reload

Verification

• cargo fmt --check
• cargo check
• cargo test
• npm run build
• API smoke test for save/fetch/delete home location
• Docker dev backend/frontend log tails clean