Add standalone HoneyDueAPITests target for pure-API suites

Split the pure-API integration tests (no UI) out of the UITest target into
a dedicated standalone unit-test target that runs in seconds without launching
the simulator app.

- HoneyDueAPITests target: standalone unit-test bundle (no TEST_HOST — touches
  no app code), shares the API client/seeder/cleaner support files from the
  UITest target via explicit references, with its own shared scheme.
- MultiUserSharingTests -> HoneyDueAPITests/SharingAPITests.swift (18 tests).
  Runs in ~2.3s vs. ~40-140s per UI test.
- run_ui_tests.sh: new Phase 1b runs the API target (fast) between Seed and the
  parallel UI phase; the helper now takes a scheme so each phase targets the
  right one; summary reports the API result.

Both targets build green; SharingAPITests passes (18/18) against the live stack.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

iosApp/honeyDue.xcodeproj/xcshareddata/xcschemes/HoneyDueAPITests.xcscheme

@@ -0,0 +1,68 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1600"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "E9D862A585C17DD92D22D303"
+               BuildableName = "HoneyDueAPITests.xctest"
+               BlueprintName = "HoneyDueAPITests"
+               ReferencedContainer = "container:honeyDue.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+      </BuildActionEntries>
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "E9D862A585C17DD92D22D303"
+               BuildableName = "HoneyDueAPITests.xctest"
+               BlueprintName = "HoneyDueAPITests"
+               ReferencedContainer = "container:honeyDue.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>