refactor: use username variable consistently

Replaced hardcoded "h" username references with variables:
- hosts/vm: use username variable for secrets.username
- home configs: use username variable in bash initExtra paths
- keepassxc: update comment to use $HOME instead of /home/h

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

home/hosts/andromache/default.nix

@@ -37,12 +37,12 @@ in
       enable = true;
       enableCompletion = true;
       initExtra = ''
-        for f in /home/h/.bashrc.d/*; do
+        for f in /home/${username}/.bashrc.d/*; do
           [ -f "$f" ] && source "$f"
         done
 
-        source /home/h/.bash_aliases/all
-        source /home/h/.bash_aliases/lang-js
+        source /home/${username}/.bash_aliases/all
+        source /home/${username}/.bash_aliases/lang-js
 
         # host-specific config goes here
         # ...

home/hosts/astyanax/default.nix

@@ -32,12 +32,12 @@ in
       enable = true;
       enableCompletion = true;
       initExtra = ''
-        for f in /home/h/.bashrc.d/*; do
+        for f in /home/${username}/.bashrc.d/*; do
           [ -f "$f" ] && source "$f"
         done
 
-        source /home/h/.bash_aliases/all
-        source /home/h/.bash_aliases/lang-js
+        source /home/${username}/.bash_aliases/all
+        source /home/${username}/.bash_aliases/lang-js
 
         # host-specific config goes here
         # ...

home/modules/keepassxc.nix

@@ -7,5 +7,5 @@
       Browser.Enabled = true;
     };
   };
-  # programs.firefox.nativeMessagingHosts = [ pkgs.keepassxc ]; # FIXME: Resolve 'Access error for config file /home/h/.config/keepassxc/keepassxc.ini' error
+  # programs.firefox.nativeMessagingHosts = [ pkgs.keepassxc ]; # FIXME: Resolve 'Access error for config file $HOME/.config/keepassxc/keepassxc.ini' error
 }

hosts/vm/default.nix

@@ -33,7 +33,7 @@ in
     })
   ];
 
-  secrets.username = "h";
+  secrets.username = username;
 
   environment.systemPackages = [ inputs.nvim.packages.x86_64-linux.nvim ];