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

public/fonts/figlet-fonts/README.md

@@ -0,0 +1,11 @@
+```
+┏━╸╻┏━╸╻  ┏━╸╺┳╸   ┏━╸┏━┓┏┓╻╺┳╸┏━┓
+┣╸ ┃┃╺┓┃  ┣╸  ┃    ┣╸ ┃ ┃┃┗┫ ┃ ┗━┓
+╹  ╹┗━┛┗━╸┗━╸ ╹    ╹  ┗━┛╹ ╹ ╹ ┗━┛
+```
+
+my collection of ascii art fonts for [figlet](http://www.figlet.org/) or [toilet](http://caca.zoy.org/wiki/toilet). 
+
+install files to `/usr/share/figlet/` or `/usr/share/figlet/fonts/`.
+
+View example text at [examples](Examples.md).