feat(ui): modernize nvim with fzf-lua, snacks dashboard, and p10k-style statusline

- Replace Snacks picker with fzf-lua for LSP navigation (gd, gr, gi, gt)
- Add fzf-lua plugin with LSP-optimized settings
- Fix Mason inconsistencies (add eslint, gopls to ensure_installed)
- Replace alpha-nvim with Snacks dashboard (shared config)
- Create dashboard_config.lua for DRY dashboard settings
- Modernize lualine with p10k-rainbow style and solid backgrounds
- Enhance bufferline with LSP diagnostics and modern styling
- Update noice with centered cmdline/search and modern icons
- Add global rounded borders for floating windows
- Improve indent-blankline with scope highlighting
- Add return-to-dashboard on last buffer close
- Create performance_monitor module

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

.gitignore

@@ -24,3 +24,7 @@ session.vim
 
 # Local configuration overrides
 local.lua
+
+# Codetyper.nvim - AI coding partner files
+*.coder.*
+.coder/