Update Neon colors and show color circles in theme picker

- Update NeonMoodTint to use synthwave colors matching Neon voting style
  (cyan, lime, yellow, orange, magenta)
- Replace text label with 5 color circles in theme preview Colors row
- Remove unused textColor customization code and picker views
- Add .id(moodTint) to Month/Year views for color refresh
- Clean up various unused color-related code

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Shared/Random.swift

@@ -58,9 +58,11 @@ class Random {
         return newValue
     }
     
+    /// Cached month symbols to avoid creating DateFormatter repeatedly
+    private static let monthSymbols: [String] = DateFormatter().monthSymbols
+
     static func monthName(fromMonthInt: Int) -> String {
-        let monthName = DateFormatter().monthSymbols[fromMonthInt-1]
-        return monthName
+        return monthSymbols[fromMonthInt-1]
     }
     
     static var existingDayFormat = [NSNumber: String]()
@@ -165,7 +167,15 @@ extension Color {
 }
 
 extension String {
+    /// Cache for rendered emoji images to avoid expensive re-rendering
+    private static var textToImageCache = [String: UIImage]()
+
     func textToImage() -> UIImage? {
+        // Return cached image if available
+        if let cached = Self.textToImageCache[self] {
+            return cached
+        }
+
         let nsString = (self as NSString)
         let font = UIFont.systemFont(ofSize: 100) // you can change your font size here
         let stringAttributes = [NSAttributedString.Key.font: font]
@@ -178,7 +188,12 @@ extension String {
         let image = UIGraphicsGetImageFromCurrentImageContext() // create image from context
         UIGraphicsEndImageContext() //  end image context
 
-        return image ?? UIImage()
+        let result = image ?? UIImage()
+
+        // Cache the rendered image
+        Self.textToImageCache[self] = result
+
+        return result
     }
 }
 
@@ -218,6 +233,179 @@ extension UIColor {
 }
 #endif
 
+// MARK: - Date Formatting Cache
+
+/// High-performance date formatting cache to eliminate repeated ICU Calendar operations.
+/// Caches formatted date strings keyed by (date's day start, format type).
+final class DateFormattingCache {
+    static let shared = DateFormattingCache()
+
+    enum Format: Int {
+        case day                    // "15"
+        case weekdayWide            // "Monday"
+        case weekdayAbbreviated     // "Mon"
+        case weekdayWideDay         // "Monday 15"
+        case monthWide              // "January"
+        case monthAbbreviated       // "Jan"
+        case monthAbbreviatedDay    // "Jan 15"
+        case monthAbbreviatedYear   // "Jan 2025"
+        case monthWideYear          // "January 2025"
+        case weekdayAbbrevMonthAbbrev // "Mon Jan"
+        case weekdayWideMonthAbbrev   // "Monday Jan"
+        case yearMonthDayDigits       // "2025/01/15"
+        case dateMedium               // "Jan 15, 2025" (dateStyle = .medium)
+        case dateFull                 // "Monday, January 15, 2025" (dateStyle = .full)
+    }
+
+    private var cache = [Int: [Format: String]]()
+    private let calendar = Calendar.current
+
+    // Reusable formatters (creating DateFormatter is expensive)
+    private lazy var dayFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "d"
+        return f
+    }()
+
+    private lazy var weekdayWideFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "EEEE"
+        return f
+    }()
+
+    private lazy var weekdayAbbrevFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "EEE"
+        return f
+    }()
+
+    private lazy var weekdayWideDayFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "EEEE d"
+        return f
+    }()
+
+    private lazy var monthWideFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMMM"
+        return f
+    }()
+
+    private lazy var monthAbbrevFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMM"
+        return f
+    }()
+
+    private lazy var monthAbbrevDayFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMM d"
+        return f
+    }()
+
+    private lazy var monthAbbrevYearFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMM yyyy"
+        return f
+    }()
+
+    private lazy var monthWideYearFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "MMMM yyyy"
+        return f
+    }()
+
+    private lazy var weekdayAbbrevMonthAbbrevFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "EEE MMM"
+        return f
+    }()
+
+    private lazy var weekdayWideMonthAbbrevFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "EEEE MMM"
+        return f
+    }()
+
+    private lazy var yearMonthDayDigitsFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateFormat = "yyyy/MM/dd"
+        return f
+    }()
+
+    private lazy var dateMediumFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateStyle = .medium
+        return f
+    }()
+
+    private lazy var dateFullFormatter: DateFormatter = {
+        let f = DateFormatter()
+        f.dateStyle = .full
+        return f
+    }()
+
+    private init() {}
+
+    /// Get cached formatted string for a date
+    func string(for date: Date, format: Format) -> String {
+        let dayKey = dayIdentifier(for: date)
+
+        // Check cache
+        if let formatCache = cache[dayKey], let cached = formatCache[format] {
+            return cached
+        }
+
+        // Format and cache
+        let formatted = formatDate(date, format: format)
+
+        if cache[dayKey] == nil {
+            cache[dayKey] = [:]
+        }
+        cache[dayKey]?[format] = formatted
+
+        return formatted
+    }
+
+    private func dayIdentifier(for date: Date) -> Int {
+        // Use days since reference date as unique key
+        Int(calendar.startOfDay(for: date).timeIntervalSinceReferenceDate / 86400)
+    }
+
+    private func formatDate(_ date: Date, format: Format) -> String {
+        switch format {
+        case .day:
+            return dayFormatter.string(from: date)
+        case .weekdayWide:
+            return weekdayWideFormatter.string(from: date)
+        case .weekdayAbbreviated:
+            return weekdayAbbrevFormatter.string(from: date)
+        case .weekdayWideDay:
+            return weekdayWideDayFormatter.string(from: date)
+        case .monthWide:
+            return monthWideFormatter.string(from: date)
+        case .monthAbbreviated:
+            return monthAbbrevFormatter.string(from: date)
+        case .monthAbbreviatedDay:
+            return monthAbbrevDayFormatter.string(from: date)
+        case .monthAbbreviatedYear:
+            return monthAbbrevYearFormatter.string(from: date)
+        case .monthWideYear:
+            return monthWideYearFormatter.string(from: date)
+        case .weekdayAbbrevMonthAbbrev:
+            return weekdayAbbrevMonthAbbrevFormatter.string(from: date)
+        case .weekdayWideMonthAbbrev:
+            return weekdayWideMonthAbbrevFormatter.string(from: date)
+        case .yearMonthDayDigits:
+            return yearMonthDayDigitsFormatter.string(from: date)
+        case .dateMedium:
+            return dateMediumFormatter.string(from: date)
+        case .dateFull:
+            return dateFullFormatter.string(from: date)
+        }
+    }
+}
+
 extension Bundle {
     var appName: String {
         return infoDictionary?["CFBundleName"] as! String