refactor: remove verified dead code across data, UI, and resources (#680)

* refactor: remove unused dead code across data, UI, and resources

* fix: resolve dangling references left by dead-code removal

Restore empty object Motion (braces required) and remove the 12 stale
test usages that still called the now-deleted production symbols:
- ServerStoreTest: removeServer/switchToServer tests
- ServerEndpointTest: isCleartext assertions
- ConnectViewModelTest: onHostChange/onPortChange tests + 3 dropped R.string refs
- SettingsViewModelTest: renameProfile tests + clearNavigateToLogin
- E2eIntegrationTest: previewSkill tests + onHostChange/onPortChange calls

Verified locally: compileDebugUnitTestKotlin + 48 tests pass.

* fix: remove unused imports flagged by ktlint

Drops 4 no-longer-referenced imports left by the dead-code removal:
- HermesApiService: SkillScanResponse (scanHubSkill removed)
- ServerEndpointTest: assertFalse, assertTrue (isCleartext assertions dropped)
- SettingsViewModelTest: assertFalse (rename tests removed)

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/model/BillingModels.kt

@@ -125,11 +125,6 @@ data class UsageBar(
 
 // ── subscription.preview ──────────────────────────────────────────────────
 
-@Serializable
-data class SubscriptionPreviewRequest(
-    val subscription_type_id: String,
-)
-
 @Serializable
 data class SubscriptionPreviewResponse(
     val ok: Boolean? = null,
@@ -184,11 +179,6 @@ data class SubscriptionResumeResponse(
 
 // ── subscription.upgrade ──────────────────────────────────────────────────
 
-@Serializable
-data class SubscriptionUpgradeRequest(
-    val subscription_type_id: String,
-)
-
 @Serializable
 data class SubscriptionUpgradeResponse(
     val ok: Boolean? = null,