feat: consent screen, reminder system, medical metrics, sex field, design tokens, code quality

A. Reminder: ReminderService (AlarmManager chain), ReminderSettingsView,
   bell icon in Piezo top bar, reschedule on catheterization
B. Consent: ConsentView (3 mandatory items), onboarding→consent→registration flow,
   persistent consent storage, sex field in User + Registration Step 2
C. Diary: 24hUV, NUV, NPI, max capacity, day/night frequency metrics card
D. Design: DesignTokens.kt, 48dp touch targets, DonutChart semantics, pressScale modifier
E. Quality: BuildConfig.DEBUG log wrapping, DateFormatter caching, background I/O for diary store

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/main/java/com/example/medilightv2android/managers/NirsManager.kt

@@ -6,6 +6,7 @@ import androidx.compose.runtime.mutableStateOf
 import com.example.medilightv2android.models.NirsMagResponse
 import com.example.medilightv2android.models.NirsMcjPacket
 import com.example.medilightv2android.models.NirsConstants
+import com.example.medilightv2android.BuildConfig
 import com.example.medilightv2android.models.NirsOxyResult
 
 class NirsManager private constructor() {
@@ -42,7 +43,7 @@ class NirsManager private constructor() {
         currentOxy.value = result.oxyFiltered
         sampleCount.intValue++
 
-        if (sampleCount.intValue <= 3 || sampleCount.intValue % 50 == 0) {
+        if (BuildConfig.DEBUG && (sampleCount.intValue <= 3 || sampleCount.intValue % 50 == 0)) {
             android.util.Log.d("NirsManager", "Sample #${sampleCount.intValue}: " +
                 "hasGain=${calcEngine.hasGain}, " +
                 "led[0..5]=${packet.ledValues.take(6)}, " +