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>

lua/cargdev/core/dashboard_config.lua

@@ -0,0 +1,66 @@
+-- Shared dashboard configuration for alpha-nvim and snacks.dashboard
+local M = {}
+
+M.header = {
+  "  ██████╗ █████╗ ██████╗  ██████╗ ██████╗ ███████╗██╗   ██╗ ",
+  "  █╔════╝██╔══██╗██╔══██╗██╔════╝ ██╔══██╗██╔════╝██║   ██║ ",
+  "  █║     ███████║██████╔╝██║  ███╗██║  ██║█████╗  ██║   ██║ ",
+  "  █║     ██╔══██║██╔══██╗██║   ██║██║  ██║██╔══╝  ╚██╗ ██╔╝ ",
+  "  ██████╗██║  ██║██║  ██║╚██████╔╝██████╔╝███████╗ ╚████╔╝  ",
+  "  ╚═════╝╚═╝  ╚═╝╚═╝  ╚═╝ ╚═════╝ ╚═════╝ ╚══════╝  ╚═══╝   ",
+  "                                                     ",
+  "  ███╗   ██╗███████╗ ██████╗ ██╗   ██╗██╗███╗   ███╗ ",
+  "  ████╗  ██║██╔════╝██╔═══██╗██║   ██║██║████╗ ████║ ",
+  "  ██╔██╗ ██║█████╗  ██║   ██║██║   ██║██║██╔████╔██║ ",
+  "  ██║╚██╗██║██╔══╝  ██║   ██║╚██╗ ██╔╝██║██║╚██╔╝██║ ",
+  "  ██║ ╚████║███████╗╚██████╔╝ ╚████╔╝ ██║██║ ╚═╝ ██║ ",
+  "  ╚═╝  ╚═══╝╚══════╝ ╚═════╝   ╚═══╝  ╚═╝╚═╝     ╚═╝ ",
+}
+
+-- Menu items (single column)
+M.menu_items = {
+  { key = "f", icon = " ", desc = "Find File", action = ":FzfLua files" },
+  { key = "n", icon = " ", desc = "New File", action = ":ene | startinsert" },
+  { key = "g", icon = " ", desc = "Find Text", action = ":FzfLua live_grep" },
+  { key = "r", icon = " ", desc = "Recent Files", action = ":FzfLua oldfiles" },
+  { key = "t", icon = " ", desc = "File Tree", action = ":NvimTreeToggle" },
+  { key = "L", icon = "󰒲 ", desc = "Lazy", action = ":Lazy" },
+  { key = "m", icon = " ", desc = "Mason", action = ":Mason" },
+  { key = "q", icon = " ", desc = "Quit", action = ":qa" },
+}
+
+-- Get header as string (for snacks)
+function M.get_header_string()
+  return table.concat(M.header, "\n")
+end
+
+-- Helper to convert menu items to snacks format
+local function to_snacks_keys(items)
+  local keys = {}
+  for _, item in ipairs(items) do
+    table.insert(keys, {
+      icon = item.icon,
+      key = item.key,
+      desc = item.desc,
+      action = item.action,
+    })
+  end
+  return keys
+end
+
+-- Get snacks dashboard keys format
+function M.get_snacks_keys()
+  return to_snacks_keys(M.menu_items)
+end
+
+-- Get alpha buttons (requires alpha dashboard module)
+function M.get_alpha_buttons(dashboard)
+  local buttons = {}
+  for _, item in ipairs(M.menu_items) do
+    local cmd = item.action:gsub("^:", "<cmd>") .. "<CR>"
+    table.insert(buttons, dashboard.button(item.key, item.icon .. " " .. item.desc, cmd))
+  end
+  return buttons
+end
+
+return M