fix: don't show "unloads in" when keep_alive=-1

With the radagast server flipped to OLLAMA_KEEP_ALIVE=-1, /api/ps
returns expires_at as year 4001 (effectively forever), which the
old code rendered as "Hot: gemma2:9b — unloads in 17500000h". Add
a 7-day threshold to formatRemaining(); anything beyond that just
shows the model name with no expiry suffix.

CHANGELOG.md

@@ -7,6 +7,9 @@ Versioning: [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Fixed
+- "Hot: …" status no longer claims "unloads in X" when the server's `keep_alive` is `-1` (Ollama returns an absurd year-4001 `expires_at`). Threshold: any expiry >7 days drops the suffix and just shows the model name.
+
 ## [0.2.0] - 2026-06-09
 
 ### Added