Convert ODI mappings and packages to BigQuery SQL

<!-- ODI Mapping: Load_Claims_Fact -->
<Mapping name="Load_Claims_Fact">
  <Source schema="STAGING"
         table="STG_CLAIMS"/>
  <Target schema="DW"
         table="FACT_CLAIMS"/>
  <Join condition="SRC.CLAIM_ID = TGT.CLAIM_ID"/>
  <Filter>
    SRC.PROC_DT BETWEEN :START_DT AND :END_DT
  </Filter>
  <Expression target="CLAIM_STATUS">
    DECODE(STATUS,'O','Open','D','Denied',
           'P','Paid','S','Settled','Pending')
  </Expression>
  <Expression target="NET_AMOUNT">
    NVL(BILLED_AMT,0) - NVL(ADJUST_AMT,0)
  </Expression>
  <Expression target="PROC_YEAR">
    TO_CHAR(PROC_DT, 'YYYY')
  </Expression>
  <IKM name="IKM SQL to SQL Append"
       FLOW_CONTROL="true"
       COMMIT="true"/>
</Mapping>

-- ODI IKM SQL to SQL Append → BigQuery MERGE

-- Partitioned target table (replaces Oracle partitioning)
-- CREATE TABLE dw.fact_claims (...)
-- PARTITION BY DATE_TRUNC(proc_dt, MONTH)
-- CLUSTER BY claim_status;

MERGE INTO `project.dw.fact_claims` AS tgt
USING (
  SELECT
    claim_id,
    proc_dt,
    CASE status
      WHEN 'O' THEN 'Open'
      WHEN 'D' THEN 'Denied'
      WHEN 'P' THEN 'Paid'
      WHEN 'S' THEN 'Settled'
      ELSE 'Pending'
    END AS claim_status,
    COALESCE(billed_amt, 0)
      - COALESCE(adjust_amt, 0) AS net_amount,
    CAST(FORMAT_DATE('%Y', proc_dt) AS STRING)
      AS proc_year
  FROM `project.staging.stg_claims`
  WHERE proc_dt BETWEEN @start_dt AND @end_dt
) AS src
ON tgt.claim_id = src.claim_id
WHEN MATCHED THEN UPDATE SET
  tgt.claim_status = src.claim_status,
  tgt.net_amount   = src.net_amount,
  tgt.proc_year    = src.proc_year,
  tgt.proc_dt      = src.proc_dt
WHEN NOT MATCHED THEN INSERT
  (claim_id, proc_dt, claim_status,
   net_amount, proc_year)
VALUES
  (src.claim_id, src.proc_dt, src.claim_status,
   src.net_amount, src.proc_year);

-- Scheduled Query replaces ODI package scheduling
-- Schedule: Every 2 hours via BigQuery Scheduled Queries
-- Parameters: @start_dt, @end_dt passed at runtime