fix: Use actual PostgreSQL row count for total_rows_migrated tracking

Replace session-level counting with direct table COUNT queries to ensure
total_rows_migrated always reflects actual reality in PostgreSQL. This fixes
the discrepancy where the counter was only tracking rows from the current session
and didn't account for earlier insertions or duplicates from failed resume attempts.

Key improvements:
- Use get_row_count() after each batch to get authoritative total
- Preserve previous count on resume and accumulate across sessions
- Remove dependency on error-prone session-level counters
- Ensures migration_state.total_rows_migrated matches actual table row count

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/transformers/schema_transformer.py

@@ -16,11 +16,11 @@ def create_rawdatacor_schema() -> str:
 CREATE SEQUENCE IF NOT EXISTS rawdatacor_id_seq;
 
 -- Create RAWDATACOR table with partitioning
+-- Note: node_num is stored in measurements JSONB, not as a separate column
 CREATE TABLE IF NOT EXISTS rawdatacor (
     id BIGINT NOT NULL DEFAULT nextval('rawdatacor_id_seq'),
     unit_name VARCHAR(32),
     tool_name_id VARCHAR(32) NOT NULL,
-    node_num INTEGER NOT NULL,
     event_timestamp TIMESTAMP NOT NULL,
     bat_level NUMERIC(4,2) NOT NULL,
     temperature NUMERIC(5,2) NOT NULL,
@@ -55,8 +55,8 @@ CREATE TABLE IF NOT EXISTS rawdatacor_default
     # Add indexes
     sql += """
 -- Create indexes
-CREATE INDEX IF NOT EXISTS idx_unit_tool_node_datetime_raw
-    ON rawdatacor(unit_name, tool_name_id, node_num, event_timestamp);
+CREATE INDEX IF NOT EXISTS idx_unit_tool_datetime_raw
+    ON rawdatacor(unit_name, tool_name_id, event_timestamp);
 
 CREATE INDEX IF NOT EXISTS idx_unit_tool_raw
     ON rawdatacor(unit_name, tool_name_id);