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/llm-config.lua

@@ -0,0 +1,67 @@
+local llm_endpoint = "https://llm-api.va.reichard.io"
+-- local llm_assistant_model = "gpt-oss-20b-thinking"
+-- local llm_infill_model = "qwen2.5-coder-3b-instruct"
+
+-- Available models: qwen3-30b-2507-instruct, qwen2.5-coder-3b-instruct
+local llm_assistant_model = "qwen3-30b-2507-instruct"
+local llm_infill_model = llm_assistant_model
+
+-- Default Llama - Toggle Llama & Copilot
+-- vim.g.copilot_filetypes = { ["*"] = false }
+local current_mode = "copilot"
+local function toggle_llm_fim_provider()
+	if current_mode == "llama" then
+		vim.g.copilot_filetypes = { ["*"] = true }
+		vim.cmd("Copilot enable")
+		vim.cmd("LlamaDisable")
+		current_mode = "copilot"
+		vim.notify("Copilot FIM enabled", vim.log.levels.INFO)
+	else
+		vim.g.copilot_filetypes = { ["*"] = true }
+		vim.cmd("Copilot disable")
+		vim.cmd("LlamaEnable")
+		current_mode = "llama"
+		vim.notify("Llama FIM enabled", vim.log.levels.INFO)
+	end
+end
+
+-- OpenCode Configuration
+vim.g.opencode_opts = {
+	provider = {
+		enabled = "snacks",
+		snacks = {
+			win = {
+				-- position = "float",
+				enter = true,
+				width = 0.5,
+				-- height = 0.75,
+			},
+			start_insert = true,
+			auto_insert = true,
+		}
+	}
+}
+
+-- Copilot Configuration
+vim.g.copilot_no_tab_map = true
+
+-- LLama LLM FIM
+vim.g.llama_config = {
+	endpoint = llm_endpoint .. "/infill",
+	model = llm_infill_model,
+	n_predict = 2048,
+	ring_n_chunks = 32,
+	enable_at_startup = false,
+}
+
+-- Create KeyMaps
+vim.keymap.set("n", "<leader>af", toggle_llm_fim_provider, { desc = "Toggle FIM (Llama / Copilot)" })
+vim.keymap.set({ "n", "x" }, "<leader>ai", function() require("opencode").ask("@this: ", { submit = true }) end,
+	{ desc = "Ask OpenCode" })
+vim.keymap.set({ "n", "x" }, "<leader>aa", function() require("opencode").select() end,
+	{ desc = "Execute OpenCode Action" })
+vim.keymap.set({ "n", "t" }, "<leader>at", function() require("opencode").toggle() end, { desc = "Toggle OpenCode" })
+vim.keymap.set('i', '<C-J>', 'copilot#Accept("\\<CR>")', {
+	expr = true,
+	replace_keycodes = false
+})