feat(nvim): reorganize and modernize Neovim configuration

- Remove deprecated config files: git-ref.lua, git-signs.lua, diffview-config.lua, lsp-lines-config.lua, neotree-config.lua, fidget-spinner.lua, silicon-config.lua, telescope-config.lua, llm.lua
- Add new configuration files: diagnostics-config.lua, git-config.lua, llm-config.lua, snacks-config.lua
- Update existing config files: base.lua, dap-config.lua, init.lua, lsp-config.lua, lualine-config.lua, noice-config.lua, octo-config.lua, toggleterm-config.lua, which-key-config.lua
- Update nvim and opencode module configurations

modules/home/programs/terminal/nvim/config/lua/base.lua

@@ -6,7 +6,7 @@
 vim.cmd("colorscheme catppuccin-mocha")
 
 -- Set User Shell
-vim.o.shell = "/usr/bin/env bash"
+vim.o.shell = require("nix-vars").bash
 
 -- Set Leader
 vim.keymap.set("n", "<Space>", "<Nop>", { silent = true })
@@ -38,35 +38,3 @@ vim.opt.shiftwidth = 2
 vim.opt.foldmethod = "indent"
 vim.opt.foldnestmax = 10
 vim.opt.foldlevel = 2
-
--- Diagnostics Mappings
-local diagnostics_active = true
-local toggle_diagnostics = function()
-	diagnostics_active = not diagnostics_active
-	if diagnostics_active then
-		vim.diagnostic.enable()
-	else
-		vim.diagnostic.disable()
-	end
-end
-
-local diagnostics_loclist_active = false
-local toggle_diagnostics_loclist = function()
-	diagnostics_loclist_active = not diagnostics_loclist_active
-	if diagnostics_loclist_active then
-		vim.diagnostic.setloclist()
-	else
-		vim.cmd("lclose")
-	end
-end
-
-local opts = { noremap = true, silent = true }
-vim.keymap.set("n", "<leader>qt", toggle_diagnostics, opts)
-vim.keymap.set("n", "<leader>qN", function()
-	vim.diagnostic.goto_prev({ float = false })
-end, opts)
-vim.keymap.set("n", "<leader>qn", function()
-	vim.diagnostic.goto_next({ float = false })
-end, opts)
-vim.keymap.set("n", "<leader>qq", toggle_diagnostics_loclist, opts)
-vim.keymap.set("n", "<leader>qe", vim.diagnostic.open_float, opts)