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>

cron/formatter.py

@@ -0,0 +1,55 @@
+"""Format cron job results as Matrix messages (markdown)."""
+
+
+def format_search_results(job_name: str, results: list[dict]) -> str:
+    """Format Brave Search results as a markdown message for Matrix."""
+    count = len(results)
+    lines = [f"**{job_name}** \u2014 {count} new result{'s' if count != 1 else ''}:\n"]
+
+    for i, r in enumerate(results, 1):
+        title = r.get("title", "Untitled")
+        url = r.get("url", "")
+        desc = r.get("description", "")
+        lines.append(f"{i}. **[{title}]({url})**")
+        if desc:
+            lines.append(f"   {desc}")
+        lines.append("")
+
+    lines.append(
+        "_Manage automations: https://matrixhost.eu/settings/automations_"
+    )
+    return "\n".join(lines)
+
+
+def format_listings(job_name: str, listings: list[dict]) -> str:
+    """Format browser-scraped listings as a markdown message for Matrix."""
+    count = len(listings)
+    lines = [f"**{job_name}** \u2014 {count} new listing{'s' if count != 1 else ''}:\n"]
+
+    for i, item in enumerate(listings, 1):
+        title = item.get("title", "Unknown")
+        price = item.get("price", "")
+        location = item.get("location", "")
+        url = item.get("url", "")
+        age = item.get("age", "")
+
+        line = f"{i}. **{title}**"
+        if price:
+            line += f" \u2014 {price}"
+        lines.append(line)
+
+        details = []
+        if location:
+            details.append(f"\U0001f4cd {location}")
+        if age:
+            details.append(f"\U0001f4c5 {age}")
+        if url:
+            details.append(f"[View listing]({url})")
+        if details:
+            lines.append(f"   {' \u00b7 '.join(details)}")
+        lines.append("")
+
+    lines.append(
+        "_Manage automations: https://matrixhost.eu/settings/automations_"
+    )
+    return "\n".join(lines)