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/executor.py

@@ -0,0 +1,28 @@
+"""Dispatch cron jobs to the correct executor by job_type."""
+
+import logging
+
+from .brave_search import execute_brave_search
+from .browser_executor import execute_browser_scrape
+from .reminder import execute_reminder
+
+logger = logging.getLogger(__name__)
+
+EXECUTORS = {
+    "brave_search": execute_brave_search,
+    "browser_scrape": execute_browser_scrape,
+    "reminder": execute_reminder,
+}
+
+
+async def execute_job(job: dict, send_text, matrix_client) -> dict:
+    """Execute a cron job and return a result dict for reporting."""
+    job_type = job["jobType"]
+    executor = EXECUTORS.get(job_type)
+
+    if not executor:
+        msg = f"Unknown job type: {job_type}"
+        logger.error(msg)
+        return {"status": "error", "error": msg}
+
+    return await executor(job=job, send_text=send_text, matrix_client=matrix_client)