docs: update CHANGELOG for v0.3.0

CHANGELOG.md

@@ -7,6 +7,17 @@ Format: [Keep a Changelog](https://keepachangelog.com/en/1.1.0/)
 
 ## [Unreleased]
 
+## [0.3.0] — 2026-04-24
+
+### Added
+- `nu-vm/executor.rs` — `execute_node_submit`: validates entry fee (25 NUT), creates `StoryNodeState { Pending }` in RocksDB indexed by `temp_id`
+- `nu-vm/executor.rs` — `execute_vote_register`: validates node is `VotingOpen`, locks 10 NUT stake until vote end
+- `nu-vm/executor.rs` — `execute_vote_cast`: computes weight as `√(staked) × pon_score`, appends `WeightedVote` to node
+- `nu-vm/executor.rs` — `execute_stake_op`: stake/unstake with balance and staked field updates
+- `nu-state/accessor.rs` — `StateAccessor` extended with `get_account/set_account`, `get_node/get_node_by_temp/set_node`, `lock_stake/unlock_stake/add_nft/record_vote`
+- `nu-rpc/handlers.rs` — `nu_getBlock`: reads `"block:{height}"` from RocksDB, returns serialized `Block` or null
+- `nu-vm/rewards.rs` — `SHELL_PER_NUT = 1_000`, `NUT_PER_NU = 100`, `NODE_REWARD_NUT = 100` constants; currency hierarchy Shell → NUT → NU
+
 ## [0.2.0] — 2026-04-24
 
 ### Added