Polish onboarding UI and add comprehensive test coverage

UI fixes:
- Full-width single-column card layout on all 3 screens (no multi-column grids)
- Device logos replaced with brand-representative 128x128 PNGs
- Libre card now uses same layout as wearable cards (tertiary/amber Sync color)
- "Devices" title matches "The Basics" styling (no italic)
- DOB auto-advance: cursor moves month→day→year on 2-digit entry
- CTA button switched from RNGH TouchableOpacity to Pressable (fixes
  disabled state not re-rendering)
- Remove temp force-onboarding redirect

New test suites (63 new tests):
- LibreLoginForm: 36 tests (rendering, validation, regions, submission,
  error handling, loading states, cancel, input behavior)
- Onboarding integration: 16 tests (connected device state, OAuth triggers,
  Libre credential flow, sync after auth, navigation chain)
- Onboarding edge cases: 11 tests + 1 skipped (invalid dates like Feb 30,
  profile save failure resilience, goal selection toggle, auth loading state)
- Skipped test documents bug: handleStartDecoding missing try/catch

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

Author: schwaaamp

docs/planning/test-coverage-gaps.md

@@ -0,0 +1,92 @@
+# Test Coverage Gaps — Critical Priorities
+
+**Created:** 2026-03-24
+**Context:** Audit revealed strong OAuth tracker coverage but critical gaps in credential-based auth (Libre/CGM), data transformers, and integration testing.
+
+---
+
+## Gap 1: LibreLoginForm — ZERO unit tests (HIGH PRIORITY)
+
+**File:** `mobile/src/components/FitnessTracker/LibreLoginForm.tsx` (429 lines)
+**Risk:** Only credential-based auth in the app. Completely different path from OAuth trackers. No coverage at all.
+
+### What needs testing:
+- **Rendering:** Form renders email, password, region picker, submit button
+- **Validation:** Empty email, empty password, invalid email format
+- **Region selection:** All 9 regions (US, EU, EU2, DE, FR, JP, AP, AU, CA) render and are selectable
+- **Submission flow:** Calls `libre-auth` edge function with correct payload (email, password, region)
+- **Auth header:** JWT token included in request
+- **Success path:** Calls `onSuccess` callback, invalidates `connectedDevices` query
+- **Error handling:** Invalid credentials error, network error, regional endpoint errors
+- **Loading state:** Shows spinner during auth, disables submit button
+- **Cancel:** `onCancel` callback fires, form resets
+- **Keyboard behavior:** `KeyboardAvoidingView` wraps form correctly
+
+### Test file to create:
+`mobile/src/components/FitnessTracker/__tests__/LibreLoginForm.test.tsx`
+
+### Estimated tests: ~20-25
+
+---
+
+## Gap 2: Libre/CGM data transformers — no tests (HIGH PRIORITY)
+
+**Risk:** Fitbit, Whoop, and Oura each have 3-4 transformer test files (~50+ tests). Libre has zero. CGM data flows through untested transformation code.
+
+### What needs testing:
+- Glucose reading transformation (raw API → `glucose_data` table schema)
+- Timestamp handling (display_time vs glucose_timestamp, timezone offsets)
+- Value validation (physiologically plausible glucose range filtering)
+- Alarm data transformation
+- Null/missing field handling
+- Duplicate reading deduplication
+
+### Files to investigate:
+- Check `supabase/functions/sync-libre/` for transformer code
+- Mirror the test patterns from `mobile/src/utils/fitnessTrackers/__tests__/` (Whoop/Oura/Fitbit transformers)
+
+### Estimated tests: ~15-20
+
+---
+
+## Gap 3: Onboarding + device connection E2E (MEDIUM PRIORITY)
+
+**Risk:** Current onboarding tests mock all tracker hooks. No test verifies the full flow: render screen → tap device → OAuth redirect → sync → connected state updates UI.
+
+### What needs testing:
+- **Screen 2 with connected device:** Mock `useConnectedTrackers` to return a connected device → verify "Connected" badge renders, "Sync" button hidden
+- **Screen 2 OAuth trigger:** Press device card → verify `authenticate()` called with correct provider ID
+- **Screen 2 Libre flow:** Press Libre card → verify LibreLoginForm renders → cancel returns to device list
+- **Screen 2 sync status:** After successful auth, verify "Scanning History..." badge appears
+- **Screen 1 → 2 → 3 navigation:** Full forward/back navigation chain
+
+### Test file to create:
+`mobile/src/app/(onboarding)/__tests__/onboarding-integration.test.tsx`
+
+### Estimated tests: ~10-15
+
+---
+
+## Gap 4: Onboarding edge cases (LOW PRIORITY)
+
+**Risk:** Minor — happy paths are covered but some edge cases aren't.
+
+### What needs testing:
+- **Invalid date combos:** Feb 30, Apr 31, etc. (currently only validates age range)
+- **Profile save failure:** `updateProfile` throws → user should still advance (non-blocking)
+- **Re-entry:** User kills app mid-onboarding, reopens → should resume at correct step
+- **completeOnboarding failure:** AsyncStorage write fails → graceful degradation
+- **Double-tap prevention:** Pressing "Next" rapidly doesn't navigate twice
+
+### Estimated tests: ~8-10
+
+---
+
+## Implementation Order
+
+1. **LibreLoginForm tests** — highest risk, zero coverage on a production auth flow
+2. **Onboarding integration tests** — validates the new screens work with real(ish) tracker hooks
+3. **Libre data transformers** — depends on server-side code structure, may be server-side tests
+4. **Onboarding edge cases** — lowest risk, nice-to-have hardening
+
+## Total estimated new tests: ~55-70