feat(MAT-174): Add cron job scheduler and executors

Cron package that syncs jobs from matrixhost portal API, schedules execution
with timezone-aware timing, and posts results to Matrix rooms. Includes
Brave Search, reminder, and browser scrape (placeholder) executors with
formatter. 31 pytest tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_cron_formatter.py

@@ -0,0 +1,67 @@
+"""Tests for the cron result formatter."""
+
+from cron.formatter import format_search_results, format_listings
+
+
+class TestFormatSearchResults:
+    def test_single_result(self):
+        results = [
+            {"title": "BMW X3 2018", "url": "https://example.com/1", "description": "Unfallwagen"}
+        ]
+        msg = format_search_results("BMW Scan", results)
+        assert "BMW Scan" in msg
+        assert "1 new result" in msg
+        assert "BMW X3 2018" in msg
+        assert "https://example.com/1" in msg
+        assert "Unfallwagen" in msg
+        assert "matrixhost.eu/settings/automations" in msg
+
+    def test_multiple_results(self):
+        results = [
+            {"title": "Result 1", "url": "https://a.com", "description": "Desc 1"},
+            {"title": "Result 2", "url": "https://b.com", "description": "Desc 2"},
+            {"title": "Result 3", "url": "https://c.com", "description": ""},
+        ]
+        msg = format_search_results("Test Search", results)
+        assert "3 new results" in msg
+        assert "1." in msg
+        assert "2." in msg
+        assert "3." in msg
+
+    def test_result_without_description(self):
+        results = [{"title": "No Desc", "url": "https://x.com"}]
+        msg = format_search_results("Search", results)
+        assert "No Desc" in msg
+        # Should not have empty description line
+
+
+class TestFormatListings:
+    def test_single_listing(self):
+        listings = [
+            {
+                "title": "BMW X3 2.0i",
+                "price": "\u20ac4,500",
+                "location": "Limassol",
+                "url": "https://fb.com/123",
+                "age": "2h ago",
+            }
+        ]
+        msg = format_listings("Car Scan", listings)
+        assert "Car Scan" in msg
+        assert "1 new listing" in msg
+        assert "BMW X3 2.0i" in msg
+        assert "\u20ac4,500" in msg
+        assert "Limassol" in msg
+        assert "2h ago" in msg
+        assert "https://fb.com/123" in msg
+
+    def test_listing_without_optional_fields(self):
+        listings = [{"title": "Bare Listing"}]
+        msg = format_listings("Scan", listings)
+        assert "Bare Listing" in msg
+        assert "1 new listing" in msg
+
+    def test_multiple_listings_plural(self):
+        listings = [{"title": f"Item {i}"} for i in range(5)]
+        msg = format_listings("Multi", listings)
+        assert "5 new listings" in msg