test(seo): add unit tests for sitemap export and API endpoints

- test_sitemap_export.py: 19 tests covering SEOMAP_ROUTES constants,
  build_sitemap_xml() output structure, XML validity, trailing slash
  handling, and build_robots_txt() rules + sitemap reference
- test_sitemap_api.py: 7 tests covering /sitemap.xml and /robots.txt
  endpoint status codes, content types, content validation, and
  auth-gated /regenerate endpoint

Addresses reviewer REQUEST_CHANGES: 'This needs a unit test' and
'Unit test for this type too'

backend/tests/test_sitemap_api.py

@@ -0,0 +1,55 @@
+"""Tests for sitemap API endpoints — /api/sitemap/sitemap.xml, /api/sitemap/robots.txt, /api/sitemap/regenerate."""
+
+import pytest
+from httpx import AsyncClient
+from starlette.testclient import TestClient
+
+from app.main import app
+
+
+class TestSitemapEndpoints:
+    """Tests for sitemap API routes."""
+
+    def _client(self):
+        return TestClient(app)
+
+    def test_sitemap_xml_status(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/sitemap.xml")
+        assert resp.status_code == 200
+
+    def test_sitemap_xml_content_type(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/sitemap.xml")
+        assert resp.headers["content-type"].startswith("application/xml")
+
+    def test_sitemap_xml_contains_routes(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/sitemap.xml")
+        body = resp.text
+        for path in ["/", "/about", "/schedule", "/events", "/contact"]:
+            assert f"<loc>https://kmountainflower.org{path}</loc>" in body
+
+    def test_robots_txt_status(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/robots.txt")
+        assert resp.status_code == 200
+
+    def test_robots_txt_content_type(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/robots.txt")
+        assert resp.headers["content-type"].startswith("text/plain")
+
+    def test_robots_txt_contains_rules(self):
+        client = self._client()
+        resp = client.get("/api/sitemap/robots.txt")
+        body = resp.text
+        assert "User-agent: *" in body
+        assert "Disallow: /admin" in body
+        assert "Disallow: /login" in body
+        assert "Sitemap: https://kmountainflower.org/sitemap.xml" in body
+
+    def test_regenerate_requires_auth(self):
+        client = self._client()
+        resp = client.post("/api/sitemap/regenerate")
+        assert resp.status_code in (401, 403)

backend/tests/test_sitemap_export.py

@@ -0,0 +1,113 @@
+"""Tests for sitemap_export — sitemap.xml and robots.txt generation."""
+
+import pytest
+from xml.etree import ElementTree as ET
+
+from app.sitemap_export import (
+    SEOMAP_ROUTES,
+    build_sitemap_xml,
+    build_robots_txt,
+)
+
+
+class TestSitemapRoutes:
+    """Verify the route configuration constants."""
+
+    def test_route_count(self):
+        assert len(SEOMAP_ROUTES) == 5
+
+    def test_home_route(self):
+        assert SEOMAP_ROUTES[0] == {
+            "path": "/",
+            "changefreq": "daily",
+            "priority": 1.0,
+        }
+
+    def test_all_paths_present(self):
+        paths = [r["path"] for r in SEOMAP_ROUTES]
+        expected = ["/", "/about", "/schedule", "/events", "/contact"]
+        assert paths == expected
+
+    def test_priority_range(self):
+        for route in SEOMAP_ROUTES:
+            assert 0.0 <= route["priority"] <= 1.0
+
+    def test_valid_changefreq_values(self):
+        valid = {"always", "hourly", "daily", "weekly", "monthly", "yearly", "never"}
+        for route in SEOMAP_ROUTES:
+            assert route["changefreq"] in valid
+
+
+class TestBuildSitemapXml:
+    """Tests for the sitemap XML builder."""
+
+    def test_returns_string(self):
+        result = build_sitemap_xml("https://example.com")
+        assert isinstance(result, str)
+
+    def test_contains_xml_declaration(self):
+        result = build_sitemap_xml("https://example.com")
+        assert '<?xml version="1.0" encoding="UTF-8"?>' in result
+
+    def test_contains_urlset_namespace(self):
+        result = build_sitemap_xml("https://example.com")
+        assert 'xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"' in result
+
+    def test_contains_all_routes(self):
+        result = build_sitemap_xml("https://example.com")
+        for route in SEOMAP_ROUTES:
+            assert f"<loc>https://example.com{route['path']}</loc>" in result
+
+    def test_strips_trailing_slash_from_base_url(self):
+        result = build_sitemap_xml("https://example.com/")
+        assert "https://example.com//about" not in result
+        assert "<loc>https://example.com/about</loc>" in result
+
+    def test_different_base_url(self):
+        result = build_sitemap_xml("https://mystation.org")
+        assert "https://mystation.org/schedule" in result
+        assert "https://example.com" not in result
+
+    def test_valid_xml(self):
+        result = build_sitemap_xml("https://example.com")
+        # Should parse without error
+        root = ET.fromstring(result)
+        # The root tag includes the namespace
+        assert "urlset" in root.tag
+
+    def test_contains_changefreq_and_priority(self):
+        result = build_sitemap_xml("https://example.com")
+        assert "<changefreq>daily</changefreq>" in result
+        assert "<priority>1.0</priority>" in result
+        assert "<priority>0.5</priority>" in result
+
+
+class TestBuildRobotsTxt:
+    """Tests for the robots.txt builder."""
+
+    def test_returns_string(self):
+        result = build_robots_txt("https://example.com")
+        assert isinstance(result, str)
+
+    def test_user_agent_allows_all(self):
+        result = build_robots_txt("https://example.com")
+        assert "User-agent: *" in result
+        assert "Allow: /" in result
+
+    def test_disallows_admin_and_login(self):
+        result = build_robots_txt("https://example.com")
+        assert "Disallow: /admin" in result
+        assert "Disallow: /login" in result
+
+    def test_sitemap_reference(self):
+        result = build_robots_txt("https://example.com")
+        assert "Sitemap: https://example.com/sitemap.xml" in result
+
+    def test_strips_trailing_slash(self):
+        result = build_robots_txt("https://example.com/")
+        assert "Sitemap: https://example.com//sitemap.xml" not in result
+        assert "Sitemap: https://example.com/sitemap.xml" in result
+
+    def test_different_base_url(self):
+        result = build_robots_txt("https://mystation.org")
+        assert "Sitemap: https://mystation.org/sitemap.xml" in result