Add runbook for recovering wedged units and new scripts for device management

- Created a comprehensive runbook (`wedged_unit_recovery.md`) detailing the recovery process for units stuck in a call-home loop, including symptoms, recovery steps, and explanations of the failure mode.
- Added `blind_stop.sh` script to send stop-monitoring commands in a tight loop for unresponsive devices.
- Introduced `rescue_device.sh` script to disable Auto Call Home and erase events from a busy device.
- Implemented `slow_drip.sh` script to send stop-monitoring frames at a slow rate to prevent UART overrun.
- Developed `spam_stop.sh` script to rapidly send stop-monitoring commands to a device.
- Created `watch_unit.sh` script for passive monitoring of device reachability, logging results over time.

sfm/database.py

@@ -491,6 +491,75 @@ class SeismoDb:
             )
         return cur.rowcount > 0
 
+    def delete_event(self, event_id: str) -> Optional[dict]:
+        """
+        Hard-delete one event row by id.  Returns the deleted row (so the
+        caller can clean up any on-disk files referenced by it) or None
+        if no row matched.
+        """
+        with self._connect() as conn:
+            row = conn.execute(
+                "SELECT * FROM events WHERE id = ?", (event_id,),
+            ).fetchone()
+            if row is None:
+                return None
+            conn.execute("DELETE FROM events WHERE id = ?", (event_id,))
+        return dict(row)
+
+    def delete_events_bulk(
+        self,
+        serial: Optional[str] = None,
+        from_dt: Optional[datetime.datetime] = None,
+        to_dt: Optional[datetime.datetime] = None,
+        false_trigger: Optional[bool] = None,
+        ids: Optional[list[str]] = None,
+    ) -> list[dict]:
+        """
+        Hard-delete events matching the given filters.  Returns the list
+        of deleted row dicts.  Refuses to delete with no filters at all
+        (would wipe the whole table) — raises ValueError.
+
+        Filter semantics match query_events: serial / from_dt / to_dt /
+        false_trigger combine with AND.  `ids` is an additional inclusion
+        list (event_id IN (...)); if supplied alongside other filters,
+        only rows matching all conditions are deleted.
+        """
+        clauses: list[str] = []
+        params:  list      = []
+
+        if serial:
+            clauses.append("serial = ?")
+            params.append(serial)
+        if from_dt:
+            clauses.append("timestamp >= ?")
+            params.append(from_dt.isoformat())
+        if to_dt:
+            clauses.append("timestamp <= ?")
+            params.append(to_dt.isoformat())
+        if false_trigger is not None:
+            clauses.append("false_trigger = ?")
+            params.append(1 if false_trigger else 0)
+        if ids:
+            placeholders = ",".join("?" * len(ids))
+            clauses.append(f"id IN ({placeholders})")
+            params.extend(ids)
+
+        if not clauses:
+            raise ValueError(
+                "delete_events_bulk refuses to delete with no filters "
+                "(would wipe the entire events table)"
+            )
+
+        where = "WHERE " + " AND ".join(clauses)
+
+        with self._connect() as conn:
+            rows = conn.execute(
+                f"SELECT * FROM events {where}", params,
+            ).fetchall()
+            if rows:
+                conn.execute(f"DELETE FROM events {where}", params)
+        return [dict(r) for r in rows]
+
     def update_event_review(self, event_id: str, review: dict) -> bool:
         """
         Sync derived index columns from a sidecar's `review` block.