feat: add reference tables schema and Pydantic models

Implements Step 1.4: Creates migration for species, locations, products,
feed_types, and users tables with full CHECK constraints. Adds Pydantic
models with validation for all reference types including enums for
ProductUnit and UserRole.

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

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

migrations/0001-reference-tables.sql

@@ -0,0 +1,52 @@
+-- ABOUTME: Migration 0001 - reference-tables
+-- ABOUTME: Creates the five reference tables: species, locations, products, feed_types, users.
+
+-- Species: lookup table for animal species (duck, goose, sheep)
+CREATE TABLE species (
+    code TEXT PRIMARY KEY,
+    name TEXT NOT NULL,
+    active INTEGER NOT NULL DEFAULT 1 CHECK(active IN (0, 1)),
+    created_at_utc INTEGER NOT NULL,
+    updated_at_utc INTEGER NOT NULL
+);
+
+-- Locations: physical locations (Strip 1-4, Nursery 1-4)
+CREATE TABLE locations (
+    id TEXT PRIMARY KEY CHECK(length(id) = 26),
+    name TEXT NOT NULL UNIQUE,
+    active INTEGER NOT NULL DEFAULT 1 CHECK(active IN (0, 1)),
+    created_at_utc INTEGER NOT NULL,
+    updated_at_utc INTEGER NOT NULL
+);
+
+-- Products: things that can be collected/sold (eggs, meat, etc.)
+CREATE TABLE products (
+    code TEXT PRIMARY KEY,
+    name TEXT NOT NULL,
+    unit TEXT NOT NULL CHECK(unit IN ('piece', 'kg')),
+    collectable INTEGER NOT NULL CHECK(collectable IN (0, 1)),
+    sellable INTEGER NOT NULL CHECK(sellable IN (0, 1)),
+    active INTEGER NOT NULL DEFAULT 1 CHECK(active IN (0, 1)),
+    created_at_utc INTEGER NOT NULL,
+    updated_at_utc INTEGER NOT NULL
+);
+
+-- Feed types: types of feed (starter, grower, layer)
+CREATE TABLE feed_types (
+    code TEXT PRIMARY KEY,
+    name TEXT NOT NULL,
+    default_bag_size_kg INTEGER NOT NULL CHECK(default_bag_size_kg >= 1),
+    protein_pct REAL NULL,
+    active INTEGER NOT NULL DEFAULT 1 CHECK(active IN (0, 1)),
+    created_at_utc INTEGER NOT NULL,
+    updated_at_utc INTEGER NOT NULL
+);
+
+-- Users: system users with roles
+CREATE TABLE users (
+    username TEXT PRIMARY KEY,
+    role TEXT NOT NULL CHECK(role IN ('admin', 'recorder')),
+    active INTEGER NOT NULL DEFAULT 1 CHECK(active IN (0, 1)),
+    created_at_utc INTEGER NOT NULL,
+    updated_at_utc INTEGER NOT NULL
+);