feat: manage ssh client config

Symlink .ssh/config into ~/.ssh with proper directory permissions.
Guard .gitignore so only the client config is trackable — keys and
anything else under .ssh/ can never be committed. Also drop a
redundant tmux ignore rule.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitignore

@@ -26,8 +26,11 @@ nvim.log
 
 # Ignore generated or downloaded tmux content.
 .config/tmux/**
-.config/tmux/current-theme.conf
 !.config/tmux/dragon-theme.conf
 !.config/tmux/wave-theme.conf
 !.config/tmux/tmux-cheatsheet.md
 !.config/tmux/tmux.conf
+
+# Track only the ssh client config — never keys or anything else.
+.ssh/*
+!.ssh/config

.ssh/config

@@ -0,0 +1,11 @@
+Host caddy
+  HostName 10.0.15.5
+  User brian
+  IdentityFile ~/.ssh/id_ed25519
+  IdentitiesOnly yes
+
+Host technitium
+  HostName 10.0.10.5
+  User brian
+  IdentityFile ~/.ssh/id_ed25519
+  IdentitiesOnly yes

install/lib/dotfiles.sh

@@ -11,6 +11,9 @@ link_dotfiles() {
   backup_and_link "$DOTFILES_DIR/.config/.ideavimrc" "$HOME/.ideavimrc"
   backup_and_link "$DOTFILES_DIR/.zshrc" "$HOME/.zshrc"
   backup_and_link "$DOTFILES_DIR/.gitconfig" "$HOME/.gitconfig"
+  mkdir -p "$HOME/.ssh"
+  chmod 700 "$HOME/.ssh"
+  backup_and_link "$DOTFILES_DIR/.ssh/config" "$HOME/.ssh/config"
   backup_and_link "$DOTFILES_DIR/bin/dotfiles-apply-theme" "$HOME/.local/bin/dotfiles-apply-theme"
 }