feat: initial project setup with implementation plan

- Add PLAN.md with 40-step checklist across 10 phases
- Add CLAUDE.md with project-specific instructions
- Set up nix flake with FastHTML/MonsterUI dependencies
- Create Python package skeleton (src/animaltrack)
- Vendor FastHTML and MonsterUI documentation
- Add Docker build configuration

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

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

flake.nix

@@ -0,0 +1,88 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  };
+
+  outputs = { self, nixpkgs }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      # Python with custom packages
+      python = pkgs.python313.override {
+        self = python;
+        packageOverrides = pyfinal: pyprev: {
+          # Leaf packages (no custom dependencies)
+          mistletoe = pyfinal.callPackage ./packages/mistletoe.nix { };
+          sse-starlette = pyfinal.callPackage ./packages/sse-starlette.nix { };
+          fastcore = pyfinal.callPackage ./packages/fastcore.nix { };
+
+          # Second level (depend on leaf packages)
+          apswutils = pyfinal.callPackage ./packages/apswutils.nix { };
+          fastlite = pyfinal.callPackage ./packages/fastlite.nix { };
+          fastmigrate = pyfinal.callPackage ./packages/fastmigrate.nix { };
+
+          # Top level (depend on second level)
+          python-fasthtml = pyfinal.callPackage ./packages/python-fasthtml.nix { };
+          monsterui = pyfinal.callPackage ./packages/monsterui.nix { };
+        };
+      };
+
+      # Shared Python environment for both dev and Docker
+      pythonEnv = python.withPackages (ps: with ps; [
+        # From nixpkgs
+        uvicorn
+        starlette
+        httpx
+        pydantic
+        pydantic-settings
+        anyio
+        beautifulsoup4
+        python-dateutil
+        oauthlib
+        itsdangerous
+        python-multipart
+        lxml
+        apsw
+        packaging
+        python-ulid
+        xxhash
+
+        # Custom packages
+        fastcore
+        apswutils
+        fastlite
+        fastmigrate
+        sse-starlette
+        python-fasthtml
+        monsterui
+        mistletoe
+
+        # Dev-only (not needed in Docker, but fine to include)
+        pytest
+        pytest-xdist
+        ruff
+      ]);
+    in
+    {
+      packages.${system} = {
+        dockerImage = import ./docker.nix { inherit pkgs pythonEnv python; };
+      };
+
+      devShells.${system}.default = pkgs.mkShell {
+        buildInputs = [
+          pythonEnv
+
+          # Tools
+          pkgs.jq
+          pkgs.sqlite
+          pkgs.skopeo  # For pushing Docker images
+        ];
+
+        shellHook = ''
+          echo "AnimalTrack development environment ready!"
+          echo "Run 'animaltrack serve' to start the app"
+        '';
+      };
+    };
+}