Add regional task templates API with climate zone lookup

Adds a new endpoint GET /api/tasks/templates/by-region/?zip= that resolves
ZIP codes to IECC climate regions and returns relevant home maintenance
task templates. Includes climate region model, region lookup service with
tests, seed data for all 8 climate zones with 50+ templates, and OpenAPI spec.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/services/region_lookup_test.go

@@ -0,0 +1,81 @@
+package services
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetClimateRegionIDByState(t *testing.T) {
+	tests := []struct {
+		name     string
+		state    string
+		expected uint
+	}{
+		{"Massachusetts → Cold (5)", "MA", 5},
+		{"Florida → Hot-Humid (1)", "FL", 1},
+		{"Arizona → Hot-Dry (2)", "AZ", 2},
+		{"Alaska → Arctic (8)", "AK", 8},
+		{"Minnesota → Very Cold (6)", "MN", 6},
+		{"Tennessee → Mixed-Humid (3)", "TN", 3},
+		{"Missouri → Mixed (4)", "MO", 4},
+		{"Unknown state → 0", "XX", 0},
+		{"Empty string → 0", "", 0},
+		{"Lowercase input", "ma", 5},
+		{"Whitespace trimmed", " TX ", 2},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := GetClimateRegionIDByState(tt.state)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestZipToState(t *testing.T) {
+	tests := []struct {
+		name     string
+		zip      string
+		expected string
+	}{
+		{"Boston MA", "02101", "MA"},
+		{"Miami FL", "33101", "FL"},
+		{"Phoenix AZ", "85001", "AZ"},
+		{"Anchorage AK", "99501", "AK"},
+		{"New York NY", "10001", "NY"},
+		{"Chicago IL", "60601", "IL"},
+		{"Houston TX", "77001", "TX"},
+		{"Denver CO", "80201", "CO"},
+		{"DC", "20001", "DC"},
+		{"Too short", "12", ""},
+		{"Empty", "", ""},
+		{"Non-numeric", "abcde", ""},
+		{"Unrecognized prefix", "00100", ""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := ZipToState(tt.zip)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestStateToClimateRegion_AllStatesPresent(t *testing.T) {
+	// All 50 states + DC should be in the map
+	allStates := []string{
+		"AL", "AK", "AZ", "AR", "CA", "CO", "CT", "DE", "FL", "GA",
+		"HI", "ID", "IL", "IN", "IA", "KS", "KY", "LA", "ME", "MD",
+		"MA", "MI", "MN", "MS", "MO", "MT", "NE", "NV", "NH", "NJ",
+		"NM", "NY", "NC", "ND", "OH", "OK", "OR", "PA", "RI", "SC",
+		"SD", "TN", "TX", "UT", "VT", "VA", "WA", "WV", "WI", "WY",
+		"DC",
+	}
+
+	for _, state := range allStates {
+		t.Run(state, func(t *testing.T) {
+			regionID := GetClimateRegionIDByState(state)
+			assert.Greater(t, regionID, uint(0), "State %s should map to a region", state)
+			assert.LessOrEqual(t, regionID, uint(8), "State %s region should be 1-8, got %d", state, regionID)
+		})
+	}
+}