feat(config): hard-delete branches for admins

DELETE /branches/<id> now removes the row, nullifies FK references, and deletes branch-specific stock/count records.

Main branch remains protected.

pos/blueprints/config_bp.py

@@ -153,7 +153,11 @@ def update_branch(branch_id):
 @config_bp.route('/branches/<int:branch_id>', methods=['DELETE'])
 @require_auth('config.edit')
 def delete_branch(branch_id):
-    """Soft-delete a branch. Only owner/admin can delete; main branch cannot be deleted."""
+    """Hard-delete a branch. Only owner/admin can delete; main branch cannot be deleted.
+
+    Related records keep their data but lose the branch reference; stock and count
+    rows tied exclusively to the branch are removed.
+    """
     if g.employee_role not in ('owner', 'admin'):
         return jsonify({'error': 'Solo administradores pueden eliminar sucursales'}), 403
 
@@ -170,7 +174,26 @@ def delete_branch(branch_id):
         cur.close(); conn.close()
         return jsonify({'error': 'No se puede eliminar la sucursal principal'}), 403
 
-    cur.execute("UPDATE branches SET is_active = false WHERE id = %s", (branch_id,))
+    # Remove branch-specific stock and count rows first.
+    cur.execute("DELETE FROM inventory_stock WHERE branch_id = %s", (branch_id,))
+    cur.execute("DELETE FROM inventory_stock_summary WHERE branch_id = %s", (branch_id,))
+    cur.execute("DELETE FROM physical_counts WHERE branch_id = %s", (branch_id,))
+
+    # Nullify every other FK reference back to branches.
+    cur.execute("""
+        SELECT c.relname::text AS tbl, a.attname::text AS col
+        FROM pg_constraint con
+        JOIN pg_class c ON c.oid = con.conrelid
+        JOIN pg_attribute a ON a.attrelid = con.conrelid AND a.attnum = ANY(con.conkey)
+        WHERE con.confrelid = 'public.branches'::regclass
+          AND con.contype = 'f'
+    """)
+    for tbl, col in cur.fetchall():
+        if tbl in ('inventory_stock', 'inventory_stock_summary', 'physical_counts'):
+            continue
+        cur.execute(f'UPDATE "{tbl}" SET "{col}" = NULL WHERE "{col}" = %s', (branch_id,))
+
+    cur.execute("DELETE FROM branches WHERE id = %s", (branch_id,))
     conn.commit()
     cur.close()
     conn.close()