refactor(env): template environment.d config and update fish aliases

Replace hardcoded config/environment.d/generic.conf with a Tera
template (environments.tmpl) rendered via mise, pulling DOTFILES_DIR,
THEME_DIR, SECOND_BRAIN, and user info from mise.toml vars.

- Add SECOND_BRAIN variable in mise.toml for the vault path
- Update fish aliases to use $SECOND_BRAIN instead of a hardcoded path
- Fix Obsidian nvim aliases with proper quoting
- Remove stale dotfiles.conf template reference

config/fish/config.fish

@@ -51,9 +51,9 @@ if status is-interactive
 
     if command -q nvim 
         set -gx EDITOR nvim
-        alias oo="cd ~/Documents/nca-notes/"
-        alias on="nvim +Obsidian new"
-        alias os="nvim +Obsidian search"
+        alias oo="cd $SECOND_BRAIN"
+        alias on="nvim '+Obsidian new'"
+        alias os="nvim '+Obsidian search'"
         alias mini="NVIM_APPNAME=mini.nvim nvim"
     end