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 Frappe.theme

@@ -0,0 +1,30 @@
+# name: 'Catppuccin Frappé'
+# url: 'https://github.com/catppuccin/fish'
+# preferred_background: 303446
+
+fish_color_normal c6d0f5
+fish_color_command 8caaee
+fish_color_param eebebe
+fish_color_keyword e78284
+fish_color_quote a6d189
+fish_color_redirection f4b8e4
+fish_color_end ef9f76
+fish_color_comment 838ba7
+fish_color_error e78284
+fish_color_gray 737994
+fish_color_selection --background=414559
+fish_color_search_match --background=414559
+fish_color_option a6d189
+fish_color_operator f4b8e4
+fish_color_escape ea999c
+fish_color_autosuggestion 737994
+fish_color_cancel e78284
+fish_color_cwd e5c890
+fish_color_user 81c8be
+fish_color_host 8caaee
+fish_color_host_remote a6d189
+fish_color_status e78284
+fish_pager_color_progress 737994
+fish_pager_color_prefix f4b8e4
+fish_pager_color_completion c6d0f5
+fish_pager_color_description 737994