Add .env backup system for Docker containers

- backup-env-files.sh: Main backup script with Gitea integration
- validate-env-backups.sh: Validation and integrity checking
- env-backup-integration.sh: Integration with existing backup system
- completions/env-backup-completion.bash: Tab completion support
- docs/env-backup-system.md: Documentation for the backup system

These scripts provide secure backup of .env files to private Gitea repository.

completions/env-backup-completion.bash

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+# env-backup-completion.bash - Bash completion for environment backup scripts
+# Source this file or copy to ~/.local/share/bash-completion/completions/
+
+_backup_env_files() {
+    local cur prev opts
+    COMPREPLY=()
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    prev="${COMP_WORDS[COMP_CWORD-1]}"
+
+    opts="--help --init --force --dry-run --restore --list --gitea-url --username"
+
+    case ${prev} in
+        --gitea-url|-g)
+            # Suggest common gitea URL patterns
+            COMPREPLY=( $(compgen -W "https://git. https://gitea. https://code." -- ${cur}) )
+            return 0
+            ;;
+        --username|-u)
+            # No completion for username
+            return 0
+            ;;
+        *)
+            ;;
+    esac
+
+    COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
+    return 0
+}
+
+_validate_env_backups() {
+    local cur prev opts
+    COMPREPLY=()
+    cur="${COMP_WORDS[COMP_CWORD]}"
+    prev="${COMP_WORDS[COMP_CWORD-1]}"
+
+    opts="--help --verbose --summary-only --missing-only --diff"
+
+    COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
+    return 0
+}
+
+# Register completion functions
+complete -F _backup_env_files backup-env-files.sh
+complete -F _validate_env_backups validate-env-backups.sh
+
+# Also register for the full path versions
+complete -F _backup_env_files ./backup-env-files.sh
+complete -F _validate_env_backups ./validate-env-backups.sh