scripts: add create-host tool for automated host configuration generation

Implements Phase 2 of the automated deployment pipeline.

This commit adds a Python CLI tool that automates the creation of NixOS host
configurations, eliminating manual boilerplate and reducing errors.

Features:
- Python CLI using typer framework with rich terminal UI
- Comprehensive validation (hostname format/uniqueness, IP subnet/uniqueness)
- Jinja2 templates for NixOS configurations
- Automatic updates to flake.nix and terraform/vms.tf
- Support for both static IP and DHCP configurations
- Dry-run mode for safe previews
- Packaged as Nix derivation and added to devShell

Usage:
  create-host --hostname myhost --ip 10.69.13.50/24

The tool generates:
- hosts/<hostname>/default.nix
- hosts/<hostname>/configuration.nix
- Updates flake.nix with new nixosConfigurations entry
- Updates terraform/vms.tf with new VM definition

All generated configurations include full system imports (monitoring, SOPS,
autoupgrade, etc.) and are validated with nix flake check and tofu validate.

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

TODO.md

@@ -50,28 +50,58 @@ Automate the entire process of creating, configuring, and deploying new NixOS ho
 
 ---
 
-### Phase 2: Host Configuration Generator
+### Phase 2: Host Configuration Generator ✅ COMPLETED
+
+**Status:** ✅ Fully implemented and tested
+**Completed:** 2025-02-01
 
 **Goal:** Automate creation of host configuration files
 
-Doesn't have to be a plain shell script, we could also use something like python, would probably make templating easier.
+**Implementation:**
+- Python CLI tool packaged as Nix derivation
+- Available as `create-host` command in devShell
+- Rich terminal UI with configuration previews
+- Comprehensive validation (hostname format/uniqueness, IP subnet/uniqueness)
+- Jinja2 templates for NixOS configurations
+- Automatic updates to flake.nix and terraform/vms.tf
 
 **Tasks:**
-- [ ] Create script `scripts/create-host-config.sh`
-  - [ ] Takes parameters: hostname, IP, CPU cores, memory, disk size
-  - [ ] Generates `/hosts/<hostname>/` directory structure from template
-  - [ ] Creates `configuration.nix` with proper hostname and networking
-  - [ ] Generates `default.nix` with standard imports
-  - [ ] Copies/links `hardware-configuration.nix` from template
-- [ ] Add host entry to `flake.nix` programmatically
-  - [ ] Parse flake.nix
-  - [ ] Insert new nixosConfiguration entry
-  - [ ] Maintain formatting
-- [ ] Generate corresponding OpenTofu configuration
-  - [ ] Create `terraform/hosts/<hostname>.tf` with VM definition
-  - [ ] Use parameters from script input
+- [x] Create Python CLI with typer framework
+  - [x] Takes parameters: hostname, IP, CPU cores, memory, disk size
+  - [x] Generates `/hosts/<hostname>/` directory structure
+  - [x] Creates `configuration.nix` with proper hostname and networking
+  - [x] Generates `default.nix` with standard imports
+  - [x] References shared `hardware-configuration.nix` from template
+- [x] Add host entry to `flake.nix` programmatically
+  - [x] Text-based manipulation (regex insertion)
+  - [x] Inserts new nixosConfiguration entry
+  - [x] Maintains proper formatting
+- [x] Generate corresponding OpenTofu configuration
+  - [x] Adds VM definition to `terraform/vms.tf`
+  - [x] Uses parameters from CLI input
+  - [x] Supports both static IP and DHCP modes
+- [x] Package as Nix derivation with templates
+- [x] Add to flake packages and devShell
+- [x] Implement dry-run mode
+- [x] Write comprehensive README
 
-**Deliverable:** Script generates all config files for a new host
+**Usage:**
+```bash
+# In nix develop shell
+create-host \
+  --hostname test01 \
+  --ip 10.69.13.50/24 \  # optional, omit for DHCP
+  --cpu 4 \               # optional, default 2
+  --memory 4096 \         # optional, default 2048
+  --disk 50G \            # optional, default 20G
+  --dry-run               # optional preview mode
+```
+
+**Files:**
+- `scripts/create-host/` - Complete Python package with Nix derivation
+- `scripts/create-host/README.md` - Full documentation and examples
+
+**Deliverable:** ✅ Tool generates all config files for a new host, validated with Nix and Terraform
 
 ---