feat: adds deployment records for seismographs.

backend/models.py

@@ -448,6 +448,41 @@ class Alert(Base):
     expires_at = Column(DateTime, nullable=True)  # Auto-dismiss after this time
 
 
+# ============================================================================
+# Deployment Records
+# ============================================================================
+
+class DeploymentRecord(Base):
+    """
+    Deployment records: tracks each time a unit is sent to the field and returned.
+
+    Each row represents one deployment. The active deployment is the record
+    with actual_removal_date IS NULL. The fleet calendar uses this to show
+    units as "In Field" and surface their expected return date.
+
+    project_ref is a freeform string for legacy/vibration jobs like "Fay I-80".
+    project_id will be populated once those jobs are migrated to proper Project records.
+    """
+    __tablename__ = "deployment_records"
+
+    id = Column(String, primary_key=True, index=True)  # UUID
+    unit_id = Column(String, nullable=False, index=True)  # FK to RosterUnit.id
+
+    deployed_date = Column(Date, nullable=True)               # When unit left the yard
+    estimated_removal_date = Column(Date, nullable=True)      # Expected return date
+    actual_removal_date = Column(Date, nullable=True)         # Filled in when returned; NULL = still out
+
+    # Project linkage: freeform for legacy jobs, FK for proper project records
+    project_ref = Column(String, nullable=True)               # e.g. "Fay I-80" (vibration jobs)
+    project_id = Column(String, nullable=True, index=True)    # FK to Project.id (when available)
+
+    location_name = Column(String, nullable=True)             # e.g. "North Gate", "VP-001"
+    notes = Column(Text, nullable=True)
+
+    created_at = Column(DateTime, default=datetime.utcnow)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+
 # ============================================================================
 # Fleet Calendar & Job Reservations
 # ============================================================================