#7675: fix: handle network interface retrieval errors in resolvePrimaryIPv4

<!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR wraps `os.networkInterfaces()` in `resolvePrimaryIPv4()` with a `try/catch` and falls back when network interface enumeration fails, preventing crashes during self-presence initialization. The change lives in `src/infra/system-presence.ts`, which seeds a local “gateway self” presence entry at module init and uses the resolved IPv4 address to populate the `ip` field and display text. <h3>Confidence Score: 4/5</h3> - This PR is likely safe to merge and reduces crash risk, with a small behavioral ambiguity around the `ip` fallback value. - The change is localized and defensive, but the new fallback path returns a hostname in a function used to populate an `ip` field, which could confuse downstream consumers or UI formatting. - src/infra/system-presence.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} **Context used:** - Context from `dashboard` - CLAUDE.md ([source](https://app.greptile.com/review/custom-context?memory=fd949e91-5c3a-4ab5-90a1-cbe184fd6ce8)) - Context from `dashboard` - AGENTS.md ([source](https://app.greptile.com/review/custom-context?memory=0d0c8278-ef8e-4d6c-ab21-f5527e322f13)) <!-- /greptile_comment -->