feat(plugins): add git-ai-commit, diffview, and reorganize keymaps

- Add AI-powered commit message generation with git-ai-commit plugin.
- Add diffview for side-by-side git diffs.
- Reorganize telescope keymaps (<leader><leader> for live_grep, <leader>/ for find_files).
- Update lazy.nvim imports to include plugins.extras.
- Add mago.nvim for PHP support.
- Update AI plugin with model configuration.

lua/plugins/extras/diffview.lua

@@ -0,0 +1,51 @@
+-- lua/plugins/extras/diffview.lua
+-- Side-by-side diff view for staged/unstaged changes across all files
+-- https://github.com/sindrets/diffview.nvim
+--
+-- Keymaps:
+--   <leader>ds  — staged changes   (git diff --cached)
+--   <leader>du  — unstaged changes (git diff)
+--   <leader>dh  — diff against HEAD
+--   <leader>dc  — close diffview
+--
+-- Inside diffview:
+--   <Tab> / <S-Tab>  — next/prev changed file
+--   [c / ]c          — prev/next hunk in file
+--   s                — stage/unstage file (in file panel)
+--   q / <leader>dc   — close
+
+return {
+  'sindrets/diffview.nvim',
+  lazy = true,
+  dependencies = { 'nvim-tree/nvim-web-devicons' },
+  cmd = { 'DiffviewOpen', 'DiffviewClose', 'DiffviewFileHistory' },
+  keys = {
+    { '<leader>ds', '<cmd>DiffviewOpen --staged<cr>',     desc = 'git [d]iff [s]taged' },
+    { '<leader>du', '<cmd>DiffviewOpen<cr>',              desc = 'git [d]iff [u]nstaged' },
+    { '<leader>dh', '<cmd>DiffviewOpen HEAD<cr>',         desc = 'git [d]iff [h]ead' },
+    { '<leader>dc', '<cmd>DiffviewClose<cr>',             desc = 'git [d]iff [c]lose' },
+  },
+  opts = {
+    enhanced_diff_hl = true,
+    view = {
+      default = {
+        layout = 'diff2_horizontal',  -- side by side
+        winbar_info = true,
+      },
+      merge_tool = {
+        layout = 'diff3_horizontal',
+        disable_diagnostics = true,
+      },
+    },
+    file_panel = {
+      listing_style = 'tree',
+      win_config = { width = 35 },
+    },
+    hooks = {
+      -- close diffview with q in any diffview buffer
+      view_opened = function()
+        vim.keymap.set('n', 'q', '<cmd>DiffviewClose<cr>', { buffer = true, silent = true })
+      end,
+    },
+  },
+}