Jul 30 - Update backend for iPad - inspector can re-inspect and create follow-up

app/models/scheduled_inspection.py

@@ -99,6 +99,20 @@ class ScheduledInspection(db.Model):
     active        = db.Column(db.Boolean, nullable=False, default=True)
     notes         = db.Column(db.Text, nullable=True)
 
+    # ── Follow-up link (phase45) ─────────────────────────────────────────────
+    # Set when this schedule was created as a follow-up of a specific completed
+    # inspection ("Schedule Follow-up" in the iPad's history detail). The
+    # inspection eventually started from this schedule inherits it as its
+    # parent_inspection_id, so it lands as a true linked re-inspection —
+    # pre-filled from the parent and clearing the parent's follow_up_required on
+    # submit. NULL = an ordinary schedule, which is what every pre-phase45 row
+    # is.
+    parent_inspection_id = db.Column(
+        db.Integer,
+        db.ForeignKey('inspections.id', ondelete='SET NULL'),
+        nullable=True, index=True,
+    )
+
     # ── Recurrence detail (phase43) ──────────────────────────────────────────
     # weekly  : CSV of Python weekday ints, e.g. '0,2,4' = Mon/Wed/Fri.
     #           NULL/empty falls back to the legacy "every 7 days" behaviour.
@@ -126,6 +140,13 @@ class ScheduledInspection(db.Model):
     template  = db.relationship('InspectionTemplate', foreign_keys=[template_id])
     inspector = db.relationship('User', foreign_keys=[inspector_id])
     creator   = db.relationship('User', foreign_keys=[created_by])
+    # Explicit foreign_keys is required, not optional: inspections and
+    # scheduled_inspections now reference each other (Inspection
+    # .scheduled_inspection_id points here, parent_inspection_id points back),
+    # so SQLAlchemy cannot infer the join for either side. Inspection
+    # .scheduled_inspection is already declared the same way.
+    parent_inspection = db.relationship('Inspection',
+                                        foreign_keys=[parent_inspection_id])
 
     FREQUENCY_LABELS = {
         'once':    'One-time',