migrate: stow → chezmoi

- restructure repo to chezmoi conventions (dot_ prefix, private_dot_ssh/)
- add nvim config (was untracked)
- encrypt restic pass.txt with age
- remove stow artifacts (.stow-local-ignore, stow package dirs)
- update bootstrap.sh to use chezmoi apply
- remove runtime files from tracking (micro buffers, zed backup)

dot_config/nvim/.neoconf.json

@@ -0,0 +1,15 @@
+{
+  "neodev": {
+    "library": {
+      "enabled": true,
+      "plugins": true
+    }
+  },
+  "neoconf": {
+    "plugins": {
+      "lua_ls": {
+        "enabled": true
+      }
+    }
+  }
+}