feat: persist and display exchange properties from agent

Add support for exchange properties sent by the agent alongside headers.
Properties flow through the same pipeline as headers: ClickHouse columns
(input_properties, output_properties) on both executions and
processor_executions tables, MergedExecution record, ChunkAccumulator
extraction, DetailService snapshot, and REST API response.

UI adds a Properties tab next to Headers in the process diagram detail
panel, with the same input/output split table layout.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/api/schema.d.ts

@@ -1945,6 +1945,8 @@ export interface components {
             outputBody: string;
             inputHeaders: string;
             outputHeaders: string;
+            inputProperties: string;
+            outputProperties: string;
             attributes: {
                 [key: string]: string;
             };