feat: add bootstrap module and update docs

- Add lua/bootstrap.lua: redirects Neovim data/state paths when running
  as root (e.g. via symlinked ~/.config/nvim) to prevent root sessions
  from conflicting with the user-level install
- Update init.lua to require("bootstrap") before any other module
- Standardize license headers across all Lua files (capitalize author,
  add SPDX-License-Identifier)
- Update README with full plugin stack section, bootstrap docs,
  machine-local override docs, qalculate dependency, and blink.cmp
  auto-rebuild note

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lua/plugins.lua

@@ -4,20 +4,8 @@
   └────────────────────────────────────────────────────────────────┘
 --]]
 
--- Copyright (C) 2026 rootiest
---
--- This program is free software: you can redistribute it and/or modify
--- it under the terms of the GNU General Public License as published by
--- the Free Software Foundation, either version 3 of the License, or
--- (at your option) any later version.
---
--- This program is distributed in the hope that it will be useful,
--- but WITHOUT ANY WARRANTY; without even the implied warranty of
--- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--- GNU General Public License for more details.
---
--- You should have received a copy of the GNU General Public License
--- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+---- Copyright (C) 2026 Rootiest
+-- SPDX-License-Identifier: GPL-3.0-or-later
 
 -- Catppuccin.nvim
 -- Eagerly load the colorscheme plugin.