feat: Phase 1 Foundation & Dashboard implementation

- Core infrastructure: Zustand store, API client with mock fallback
- Mode detection: Port 8080 (kiosk) / 9090 (remote)
- Dashboard components: RainfallCard, ClockDisplay, CommStatus
- Header components: VoltageDisplay, BatteryStatus, LoginIndicator
- Data polling with visibility awareness
- Bundle size: ~100KB gzipped

Also adds README.md and WIKI.md documentation

.planning/phases/01-foundation-dashboard/01-02-SUMMARY.md

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+# Plan 02 Summary - Header & Voltage Components
+
+**Plan:** 02  
+**Phase:** 01-foundation-dashboard  
+**Completed:** 2026-03-13
+
+---
+
+## Tasks Completed
+
+### Task 1: VoltageDisplay Component
+- Created `src/app/components/VoltageDisplay.tsx`:
+  - Props: label, voltage, className
+  - Displays voltage with one decimal place
+  - Uses Zap icon from Lucide
+  - Min-height 44px for touch targets
+
+### Task 2: BatteryStatus Component
+- Created `src/app/components/BatteryStatus.tsx`:
+  - Props: voltage, threshold (default 12.0V), className
+  - Shows color-coded status badge (HIGH/LOW)
+  - Green for >= 12V, Red for < 12V
+  - Touch-friendly (44px min)
+
+### Task 3: Modernize Header Component
+- Updated `src/app/components/Header.tsx`:
+  - Imports and uses sensor store
+  - Shows: logo, station ID, version, time, date
+  - Shows: solar voltage, battery voltage with status
+  - Shows: communication status (ASU/dBm/percentage)
+  - Shows: login status
+  - Clock updates every second with cleanup
+
+### Task 4: Touch Target Verification
+- All interactive elements have min-height 44px
+- Verified in VoltageDisplay, BatteryStatus, Header
+
+### Task 5: DashboardLayout Integration
+- DashboardLayout already uses Header component
+- Layout works correctly with sidebar
+
+---
+
+## Files Created/Modified
+
+| File | Status |
+|------|--------|
+| src/app/components/VoltageDisplay.tsx | Created |
+| src/app/components/BatteryStatus.tsx | Created |
+| src/app/components/Header.tsx | Modified |
+
+---
+
+## Component Usage
+
+```tsx
+// VoltageDisplay
+<VoltageDisplay label="Solar" voltage={12.5} />
+
+// BatteryStatus
+<BatteryStatus voltage={12.5} threshold={12.0} />
+
+// In Header
+<VoltageDisplay label="Solar" voltage={data.voltage.solar} />
+<BatteryStatus voltage={data.voltage.battery} />
+```
+
+---
+
+## Notes
+
+- Components use Tailwind CSS classes
+- Icons from Lucide React
+- Touch targets meet 44px minimum requirement
+- Status colors follow design guidelines (green/yellow/red)