Add Redemption Orderbook (ROB) incentive rewards distribution

[adacapo21]

Summary

• Introduces a new reward type — ROB (Redemption Orderbook) incentives — that distributes INDY to owners with in-range redemption positions
• Each epoch (432,000 seconds) is divided into 480 periods of 15 minutes. For each period, the configured INDY amount is distributed pro-rata based on each owner's lovelaceAmount share of total in-range positions
• Initial configuration: 500 INDY per epoch for iUSD; iBTC, iETH, iSOL are skipped (0 INDY)
• Adds a new rob CLI command and integrates ROB into the existing all and summary commands
• Produces one IndividualReward row per owner per epoch (like governance rewards), with purpose string "ROB reward for iUSD"

Changes

• indy_rewards/rob/distribution.py (new) — Core distribution logic. Iterates 480 periods, calls the analytics API for in-range redemption orders at each timestamp, groups by owner, sums lovelaceAmount, and distributes INDY pro-rata. Handles multiple positions per owner and skips periods with no in-range orders.
• indy_rewards/analytics_api/raw.py — Added redemption_orders() endpoint calling /api/v1/rewards/redemption-orders with timestamp and in_range params
• indy_rewards/time_utils.py — Added get_epoch_start_date() (returns end of previous epoch)
• indy_rewards/config.py — Added ROB_EPOCH_INDY per-iAsset configuration
• indy_rewards/cli.py — New rob command with --pkh and --outfile support; updated all and summary commands to include ROB
• indy_rewards/summary.py — Added rob_indy parameter to get_epoch_all_rewards() and get_day_all_rewards(); added "ROB reward for " handling in _split_purpose()
• tests/test_summary.py — Added ROB mock to existing test fixture to prevent real API calls
• README.md — Added ROB usage examples and updated all command description

Test plan

• Run existing test suite: pytest tests/ — all 53 tests pass, no regressions
• Manually test indy-rewards rob 608 against a completed epoch
• Verify indy-rewards summary 608 shows ROB totals alongside SP/Gov
• Verify indy-rewards all 608 includes ROB reward rows
• Verify PKH filtering works: indy-rewards rob --pkh 608
• Verify CSV output works: indy-rewards rob -o output.csv 608
• Verify periods with no in-range orders are skipped (no INDY wasted)