Add detailed partition progress logging

Log shows:
- Current partition index and total ([X/Y])
- Partition name being processed
- Number of groups consolidated per partition after completion

This helps track migration progress when processing 18 partitions,
making it easier to identify slow partitions or issues.

🤖 Generated with Claude Code

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.env.example

@@ -16,6 +16,7 @@ POSTGRES_DATABASE=migrated_db
 BATCH_SIZE=10000
 LOG_LEVEL=INFO
 DRY_RUN=false
+CONSOLIDATION_GROUP_LIMIT=50000
 
 # Performance Testing
 BENCHMARK_OUTPUT_DIR=benchmark_results