feat(#537): analytics screen — usage + per-model stats (#558)

* feat(#537): analytics screen — usage + per-model stats from /api/analytics/*

* fix(#537): address PR review — cancel-in-flight loads, retain cache on refresh, drop redundant async

* fix(#537): surface real analytics failure, mirror backend shape (period_days/tools), round-trip test

* fix(#537): tolerate float last_used_at in analytics (backend emits epoch as number)

* fix(#537): type tools[] as AnalyticsToolUsage (tool/count/percentage), render Top tools section

* fix(analytics): fix crashes and refactor tab layout

* perf(analytics): cache responses and prefetch day windows

---------

Co-authored-by: M57 <m57@hermes-control.app>

app/src/main/java/com/m57/hermescontrol/data/ws/CommandModels.kt

@@ -12,7 +12,7 @@ data class CommandCatalog(
     val sub: Map<String, List<String>> = emptyMap(),
     val canon: Map<String, String> = emptyMap(),
     val categories: List<CommandCategory> = emptyList(),
-    val skillCount: Int = 0,
+    val skillCount: Double = 0.0,
     val warning: String = "",
 )