fix: add clockProvider to CalendarProvider for test time injection (#228)

CalendarProviderReminderTest was failing because:
- CalendarProvider.getNextEventReminderTime() filters reminders using clock.currentTimeMillis()
- With test time changed to December 2023 (past) and real time being January 2026
- All reminders were filtered out as 'in the past', returning 0

Added clockProvider pattern to CalendarProvider (same as ApplicationController)
and inject test clock via CalendarProviderTestFixture.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: williscool

android/app/src/androidTest/java/com/github/quarck/calnotify/testutils/CalendarProviderTestFixture.kt

@@ -29,6 +29,9 @@ class CalendarProviderTestFixture {
     }
 
     private fun setupInitialState() {
+        // Inject test clock into CalendarProvider for deterministic time behavior
+        CalendarProvider.clockProvider = { timeProvider.testClock }
+        
         // Clear any existing settings that might affect calendar handling
         val settings = Settings(contextProvider.fakeContext)
         settings.setBoolean("enable_manual_calendar_rescan", false)
@@ -324,6 +327,9 @@ class CalendarProviderTestFixture {
      * Cleans up test resources
      */
     fun cleanup() {
+        // Reset CalendarProvider clock to prevent test pollution
+        CalendarProvider.resetClockProvider()
+        
         baseFixture.cleanup()
     }
 

android/app/src/main/java/com/github/quarck/calnotify/calendar/CalendarProvider.kt

@@ -41,9 +41,22 @@ object CalendarProvider : CalendarProviderInterface {
     private const val LOG_TAG = "CalendarProvider"
 
     /**
-     * Clock implementation for time operations
+     * Provider for Clock - enables DI for testing
      */
-    override val clock: CNPlusClockInterface = CNPlusSystemClock()
+    var clockProvider: (() -> CNPlusClockInterface)? = null
+    
+    /**
+     * Clock implementation for time operations - uses clockProvider if set, otherwise real clock
+     */
+    override val clock: CNPlusClockInterface
+        get() = clockProvider?.invoke() ?: CNPlusSystemClock()
+    
+    /**
+     * Reset clock provider - call in @After to prevent test pollution
+     */
+    fun resetClockProvider() {
+        clockProvider = null
+    }
 
     private val alertFields =
             arrayOf(