docs: move dns automation from TODO.md to nixos-improvements.md

docs/plans/nixos-improvements.md

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+# NixOS Infrastructure Improvements
+
+This document contains planned improvements to the NixOS infrastructure that are not directly part of the automated deployment pipeline.
+
+## DNS Automation
+
+**Goal:** Automatically generate DNS entries from host configurations
+
+**Approach:** Leverage Nix to generate zone file entries from flake host configurations
+
+Since most hosts use static IPs defined in their NixOS configurations, we can extract this information and automatically generate A records. This keeps DNS in sync with the actual host configs.
+
+**Tasks:**
+- [ ] Add optional CNAME field to host configurations
+  - [ ] Add `networking.cnames = [ "alias1" "alias2" ]` or similar option
+  - [ ] Document in host configuration template
+- [ ] Create Nix function to extract DNS records from all hosts
+  - [ ] Parse each host's `networking.hostName` and IP configuration
+  - [ ] Collect any defined CNAMEs
+  - [ ] Generate zone file fragment with A and CNAME records
+- [ ] Integrate auto-generated records into zone files
+  - [ ] Keep manual entries separate (for non-flake hosts/services)
+  - [ ] Include generated fragment in main zone file
+  - [ ] Add comments showing which records are auto-generated
+- [ ] Update zone file serial number automatically
+- [ ] Test zone file validity after generation
+- [ ] Either:
+  - [ ] Automatically trigger DNS server reload (Ansible)
+  - [ ] Or document manual step: merge to master, run upgrade on ns1/ns2
+
+**Deliverable:** DNS A records and CNAMEs automatically generated from host configs