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/MoodLoggingWithDataTests.swift

@@ -10,27 +10,17 @@ import XCTest
 final class MoodLoggingWithDataTests: BaseUITestCase {
     override var seedFixture: String? { "week_of_moods" }
 
-    /// With a week of data seeded, the mood header should appear if today is missing a vote.
-    /// Log a new mood and verify header disappears.
+    /// With a week of data seeded, verify at least one entry row is visible.
     func testLogMood_Average_WhenDataExists() {
         let dayScreen = DayScreen(app: app)
 
-        // The seeded data includes today (offset 0 = great).
-        // After reset + seed, today already has an entry, so header may be hidden.
-        // If the header IS visible (i.e. vote logic says "needs vote"), tap it.
-        if dayScreen.moodHeader.waitForExistence(timeout: 3) {
+        // If the header is visible (today needs a vote), log a mood
+        if dayScreen.moodHeader.waitForExistence(timeout: defaultTimeout) {
             dayScreen.logMood(.average)
-            // After logging, header should disappear (today is now voted)
             dayScreen.assertMoodHeaderHidden()
         }
 
-        // Regardless, verify at least one entry row is visible (seeded data)
-        let anyEntry = app.firstEntryRow
-        XCTAssertTrue(
-            anyEntry.waitForExistence(timeout: 5),
-            "At least one entry row should exist from seeded data"
-        )
-
-        captureScreenshot(name: "mood_logged_with_data")
+        // Verify at least one entry row exists from seeded data
+        dayScreen.assertAnyEntryExists()
     }
 }