Rewrite all UI tests following fail-fast TEST_RULES patterns

Rewrote 60+ test files to follow honeydue-style test guidelines:
- defaultTimeout=2s, navigationTimeout=5s — fail fast, no long waits
- No coordinate taps (except onboarding paged TabView swipes)
- No sleep(), no retry loops
- No guard...else { return } silent passes — XCTFail everywhere
- All elements by accessibility ID via UITestID constants
- Screen objects for all navigation/actions/assertions
- One logical assertion per test method

Added missing accessibility identifiers to app views:
- MonthView.swift: added AccessibilityID.MonthView.grid to ScrollView
- YearView.swift: added AccessibilityID.YearView.heatmap to ScrollView

Framework rewrites:
- BaseUITestCase: added session ID, localeArguments, extraLaunchArguments
- WaitHelpers: waitForExistenceOrFail, waitUntilHittableOrFail,
  waitForNonExistence, scrollIntoView, forceTap
- All 7 screen objects rewritten with fail-fast semantics
- TEST_RULES.md added with non-negotiable rules

Known remaining issues:
- OnboardingTests: paged TabView swipes unreliable on iOS 26 simulator
- SettingsLegalLinksTests: EULA/Privacy buttons too deep in DEBUG scroll
- Customization horizontal picker scrolling needs further tuning

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Tests iOS/Tests_iOSLaunchTests.swift

@@ -2,31 +2,18 @@
 //  Tests_iOSLaunchTests.swift
 //  Tests iOS
 //
-//  Created by Trey Tartt on 1/10/22.
+//  Launch test: verifies the app launches and the tab bar appears.
 //
 
 import XCTest
 
-class Tests_iOSLaunchTests: XCTestCase {
+final class Tests_iOSLaunchTests: BaseUITestCase {
 
-    override class var runsForEachTargetApplicationUIConfiguration: Bool {
-        true
-    }
+    /// Verify the app launches successfully and the tab bar is visible.
+    func testLaunch_TabBarAppears() {
+        let tabBar = TabBarScreen(app: app)
+        tabBar.assertVisible()
 
-    override func setUpWithError() throws {
-        continueAfterFailure = false
-    }
-
-    func _testLaunch() throws {
-        let app = XCUIApplication()
-        app.launch()
-
-        // Insert steps here to perform after app launch but before taking a screenshot,
-        // such as logging into a test account or navigating somewhere in the app
-
-        let attachment = XCTAttachment(screenshot: app.screenshot())
-        attachment.name = "Launch Screen"
-        attachment.lifetime = .keepAlways
-        add(attachment)
+        captureScreenshot(name: "Launch Screen")
     }
 }