Add FlightsTests target + fix AA load fetcher (Android UA version bump)

AA was silently returning nil because the server now rejects User-Agent
"Android/2025.31" with HTTP 403 ("Please update your version of the
American Airlines app"). Bumped to "2026.14" (matches the APK in
airlines/) and centralized to a constant so the next bump is one line.
Added comprehensive logging to fetchAmericanLoad (was zero) so the next
breakage won't be silent — including an explicit ⚠️ when the server
returns the "update your version" payload.

New FlightsTests target with AirlineLoadIntegrationTests — hits live
airline APIs to verify each fetcher still returns data. Per-airline
strategy:
- Try route-explorer /departures from carrier hubs for a flight in the
  next 24h (works for AA/UA/AS/B6).
- Fall back to a known-good daily flight when route-explorer doesn't
  have the carrier in its data (NK/EK/KE — ULCC + some intl carriers).
- B6/EK/NK are status-only by design (no standby data without a PNR);
  asserted as non-nil only.
- XE (JSX) skipped: needs WKWebView host.

Retries on route-explorer 429 by parsing the `retryAfter` field and
sleeping the indicated number of seconds. Static-shared client+services
across tests so the token cache survives.

Results 2026-05-26 (xcodebuild test -scheme Flights):
  ✅ AA, AS, B6, EK, KE, UA  ❌ NK  ⏭️ XE
NK (Spirit) is now broken: GetFlightInfoBI returns HTTP 403 with
{"getFlightInfoBIResult":null}. APIM key still accepted (401 without
it), but the call itself is rejected. Documented in
AIRLINE_INTEGRATION_GUIDE.md as a known regression to fix; likely
needs reverse-engineering against the current Spirit APK in airlines/.

Also: enable shared schemes in .gitignore so `xcodebuild test` works
out of the box for anyone cloning the repo.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Flights.xcodeproj/xcshareddata/xcschemes/Flights.xcscheme

@@ -0,0 +1,102 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1540"
+   version = "1.7">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+      <BuildActionEntries>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "E373C48C497D48D388BF7657"
+               BuildableName = "Flights.app"
+               BlueprintName = "Flights"
+               ReferencedContainer = "container:Flights.xcodeproj">
+            </BuildableReference>
+         </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "NO"
+            buildForProfiling = "NO"
+            buildForArchiving = "NO"
+            buildForAnalyzing = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "T1000000000000000000006A"
+               BuildableName = "FlightsTests.xctest"
+               BlueprintName = "FlightsTests"
+               ReferencedContainer = "container:Flights.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 = "T1000000000000000000006A"
+               BuildableName = "FlightsTests.xctest"
+               BlueprintName = "FlightsTests"
+               ReferencedContainer = "container:Flights.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">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "E373C48C497D48D388BF7657"
+            BuildableName = "Flights.app"
+            BlueprintName = "Flights"
+            ReferencedContainer = "container:Flights.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+      <BuildableProductRunnable
+         runnableDebuggingMode = "0">
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "E373C48C497D48D388BF7657"
+            BuildableName = "Flights.app"
+            BlueprintName = "Flights"
+            ReferencedContainer = "container:Flights.xcodeproj">
+         </BuildableReference>
+      </BuildableProductRunnable>
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>