feat: implement Figlet, Pastel, and Unit tools with a unified layout

- Add Figlet text converter with font selection and history
- Add Pastel color palette generator and manipulation suite
- Add comprehensive Units converter with category-based logic
- Introduce AppShell with Sidebar and Header for navigation
- Modernize theme system with CSS variables and new animations
- Update project configuration and dependencies

lib/pastel/stores/historyStore.ts

@@ -0,0 +1,68 @@
+import { create } from 'zustand';
+import { persist, createJSONStorage } from 'zustand/middleware';
+
+export interface ColorHistoryEntry {
+  color: string;
+  timestamp: number;
+}
+
+interface ColorHistoryState {
+  history: ColorHistoryEntry[];
+  addColor: (color: string) => void;
+  removeColor: (color: string) => void;
+  clearHistory: () => void;
+  getRecent: (limit?: number) => ColorHistoryEntry[];
+}
+
+/**
+ * Color history store with localStorage persistence
+ *
+ * Tracks up to 50 most recent colors with timestamps
+ * Automatically removes duplicates (keeps most recent)
+ * Persists across browser sessions
+ */
+export const useColorHistory = create<ColorHistoryState>()(
+  persist(
+    (set, get) => ({
+      history: [],
+
+      addColor: (color) => {
+        const normalizedColor = color.toLowerCase();
+        set((state) => {
+          // Remove existing entry if present
+          const filtered = state.history.filter(
+            (entry) => entry.color.toLowerCase() !== normalizedColor
+          );
+
+          // Add new entry at the beginning
+          const newHistory = [
+            { color: normalizedColor, timestamp: Date.now() },
+            ...filtered,
+          ].slice(0, 50); // Keep only 50 most recent
+
+          return { history: newHistory };
+        });
+      },
+
+      removeColor: (color) => {
+        const normalizedColor = color.toLowerCase();
+        set((state) => ({
+          history: state.history.filter(
+            (entry) => entry.color.toLowerCase() !== normalizedColor
+          ),
+        }));
+      },
+
+      clearHistory: () => set({ history: [] }),
+
+      getRecent: (limit = 10) => {
+        const { history } = get();
+        return history.slice(0, limit);
+      },
+    }),
+    {
+      name: 'pastel-color-history',
+      storage: createJSONStorage(() => localStorage),
+    }
+  )
+);