feat: support iteration wrapper nodes and filter overlay by selected iteration

Server:
- Add split_depth and loop_depth columns (V9 migration)
- Persist splitDepth/loopDepth with reflection fallback for older agent versions

UI:
- Detect iterations via wrapper processorTypes (loopIteration, splitIteration, multicastBranch)
- Filter overlay by selected iteration at the wrapper level
- Skip non-selected iteration wrappers entirely (wrapper + children)
- Don't add synthetic wrappers to overlay (no diagram node correspondence)

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

cameleer3-server-app/src/main/resources/db/migration/V9__resolved_endpoint_uri.sql

@@ -1 +1,3 @@
 ALTER TABLE processor_executions ADD COLUMN resolved_endpoint_uri TEXT;
+ALTER TABLE processor_executions ADD COLUMN split_depth INTEGER DEFAULT 0;
+ALTER TABLE processor_executions ADD COLUMN loop_depth INTEGER DEFAULT 0;