Lower contributor barriers: staging API / dev Firebase config

[omi-discord-vector]

Problem

Contributing to Omi has a high barrier to entry for community developers:

1. Firmware changes require purchasing a J-Link flashing kit ($20-50+) You can technically use the nRF Connect app for OTA flashing, but it's unclear if this can recover a bricked device
2. Backend changes require running your own backend locally
3. App changes can't connect to any backend — you get a bare-bones UI with no data, making it nearly impossible to test real behavior (BLE, memories, integrations, etc.)

This makes it very difficult for community members to submit meaningful PRs with proper testing evidence (screenshots, videos, debug logs).

Proposal

Consider offering one or more of the following to lower the barrier:

• Staging API environment (e.g. staging.api.omi.me) that community dev builds can hit
• Dev Firebase project config included in the repo so cloned builds can authenticate
• Docker Compose one-liner for spinning up a local backend with seed data
• Contributor docs outlining the easiest path to test each component (app, backend, firmware)

Why This Matters

Omi is open-source, but the contribution experience doesn't match that promise yet. Lowering these barriers would unlock more community PRs, faster bug fixes, and better feature contributions.

Raised by a community member in Discord (#bluetooth-connectivity-fixes).

[beastoin]

Related: #4838 (staging environment setup). This is the community-facing ask for what #4838 addresses internally.