feat: initial fish shell configuration

- Core config layered on CachyOS base with Catppuccin Mocha theming
- Fisher plugins: fzf.fish, catppuccin, autopair, replay, puffer-fish, magic-enter, spark
- Smart CLI wrappers with fallbacks (bat, lsd, btop, dust, prettyping)
- Custom functions: git, docker, network, kitty, AI session management
- Extensive abbreviation system for keyboard-driven workflows
- Secrets/local sourcing pattern for private and machine-specific config
- README with full documentation and personalization guide
- AGPLv3+ license with copyright headers on all source files

themes/Catppuccin Latte.theme

@@ -0,0 +1,30 @@
+# name: 'Catppuccin Latte'
+# url: 'https://github.com/catppuccin/fish'
+# preferred_background: eff1f5
+
+fish_color_normal 4c4f69
+fish_color_command 1e66f5
+fish_color_param dd7878
+fish_color_keyword d20f39
+fish_color_quote 40a02b
+fish_color_redirection ea76cb
+fish_color_end fe640b
+fish_color_comment 8c8fa1
+fish_color_error d20f39
+fish_color_gray 9ca0b0
+fish_color_selection --background=ccd0da
+fish_color_search_match --background=ccd0da
+fish_color_option 40a02b
+fish_color_operator ea76cb
+fish_color_escape e64553
+fish_color_autosuggestion 9ca0b0
+fish_color_cancel d20f39
+fish_color_cwd df8e1d
+fish_color_user 179299
+fish_color_host 1e66f5
+fish_color_host_remote 40a02b
+fish_color_status d20f39
+fish_pager_color_progress 9ca0b0
+fish_pager_color_prefix ea76cb
+fish_pager_color_completion 4c4f69
+fish_pager_color_description 9ca0b0