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/EntryDetailTests.swift

@@ -12,46 +12,25 @@ final class EntryDetailTests: BaseUITestCase {
 
     /// Tap an entry row -> Entry Detail sheet opens -> dismiss it.
     func testTapEntry_OpensDetailSheet_Dismiss() {
-        // Find the first entry row by identifier prefix
         let firstEntry = app.firstEntryRow
-
-        guard firstEntry.waitForExistence(timeout: 5) else {
-            XCTFail("No entry rows found in seeded data")
-            return
-        }
-
+        firstEntry.waitForExistenceOrFail(timeout: navigationTimeout, message: "No entry rows found in seeded data")
         firstEntry.tap()
 
         let detailScreen = EntryDetailScreen(app: app)
         detailScreen.assertVisible()
-
-        captureScreenshot(name: "entry_detail_open")
-
-        // Dismiss the sheet
         detailScreen.dismiss()
         detailScreen.assertDismissed()
     }
 
-    /// Open entry detail and change mood, then dismiss.
+    /// Open entry detail and change mood via the detail sheet.
     func testChangeMood_ViaEntryDetail() {
         let firstEntry = app.firstEntryRow
-
-        guard firstEntry.waitForExistence(timeout: 5) else {
-            XCTFail("No entry rows found in seeded data")
-            return
-        }
-
+        firstEntry.waitForExistenceOrFail(timeout: navigationTimeout, message: "No entry rows found in seeded data")
         firstEntry.tap()
 
         let detailScreen = EntryDetailScreen(app: app)
         detailScreen.assertVisible()
-
-        // Select a different mood (Bad)
         detailScreen.selectMood(.bad)
-
-        captureScreenshot(name: "mood_changed_to_bad")
-
-        // Dismiss
         detailScreen.dismiss()
         detailScreen.assertDismissed()
     }