feat(governance): add counter-vote support and get_proposals_by_proposer

[DammyAji]

Summary

Resolves issue #131 — upgrades the governance contract to support counter-voting and proposer-scoped proposal enumeration.

Closes #131

---

Problem

contracts/governance/src/lib.rs previously tracked only approvals. Voters had no way to signal "no", and proposers could not enumerate their own proposals for follow-up.

Changes

Vote storage upgrade

• Replaced the bare bool vote value with VoteRecord { vote_power: u32, against: bool }
• Stored under the same UserVote(proposal_id, voter) key — key schema unchanged
• Added rejections: u32 field to Proposal struct

Counter-vote support

• vote_proposal(voter, proposal_id, against: bool) now accepts direction
  • against = false → increments proposal.approvals
  • against = true → increments proposal.rejections
• A voter may only cast one vote per proposal; flipping direction is also blocked (AlreadyVoted error)
• voted event extended with against flag for off-chain indexers

get_proposals_by_proposer

• New ProposalsByProposer(Address) persistent storage key maintains a Vec<u32> of proposal IDs per proposer
• Index updated atomically inside create_proposal
• get_proposals_by_proposer(addr) -> Vec<u32> exposed on the contract; returns empty Vec for unknown addresses

Migration path (acceptance criterion)

• migrate_votes(admin, snapshot_votes: Vec<(u32, Address)>) — one-shot, admin-only function
• Operator supplies a pre-upgrade snapshot of all UserVote keys (read off-chain before re-deploy)
• Writes each entry as VoteRecord { vote_power: 1, against: false } (all pre-upgrade votes were approvals)
• Protected by MigrationDone instance-storage flag; second call panics with MigrationAlreadyDone = 11
• migration_done event emits count of migrated entries

---

Tests

15 tests total — 3 original preserved + 12 new:

Test	Covers
test_vote_against_increments_rejections	against=true increments rejections only
test_vote_for_increments_approvals_not_rejections	against=false increments approvals only
test_mixed_votes_tallied_correctly	mixed for/against tally
test_cannot_vote_twice_same_direction	duplicate vote blocked
test_cannot_flip_vote_direction	direction flip blocked
test_get_proposals_by_proposer_empty	returns empty Vec
test_get_proposals_by_proposer_single	single proposal indexed
test_get_proposals_by_proposer_multiple	multiple proposals indexed in order
test_proposals_by_proposer_are_isolated_per_address	no cross-proposer leakage
test_migrate_votes_runs_once	migration writes VoteRecord entries
test_migrate_votes_cannot_run_twice	MigrationAlreadyDone (#11) on second call
test_migrate_votes_requires_admin	Unauthorized (#3) for non-admin

---

CI Verification

All CI steps pass locally against the exact same toolchain (dtolnay/rust-toolchain@stable):

cargo fmt --all -- --check       ✅
cargo clippy --workspace -- -D warnings  ✅  (0 warnings)
cargo check --workspace --all-targets    ✅
cargo test --workspace           ✅  27 tests, 0 failed
cargo build --target wasm32-unknown-unknown --release  ✅

Merge conflicts

None — branch is based on the current tip of main (33a67ab). git merge --no-ff origin/main → Already up to date.

---

Files changed: contracts/governance/src/lib.rs

Closes #131

[DammyAji]

@snowrugar-beep please kindly review. Thank you

[snowrugar-beep]

@DammyAji resolve confliicts.

[DammyAji]

@snowrugar-beep i have resolved conflicts but i think i did something i was not supposed to do. Can you please point it out to me.

[snowrugar-beep]

Heads-up: CI was green a moment ago but this PR is no longer marked MERGEABLE, so I didn't auto-merge it. Could you rebase against main and re-push? \xf0\x9f\x99\x8c

[snowrugar-beep]

Hey \xf0\x9f\x91\x8b \xe2\x80\x94 small update: my very first note on this PR suggested the mergeable status was a transient hiccup. After more careful checking, the branch actually has merge conflicts against main now. Could you rebase against the latest main and re-push? Once that's clean we can merge right away. Thanks \xf0\x9f\x99\x8c, and apologies for the confusion in the earlier message!

[DammyAji]

@snowrugar-beep please check now and review

[snowrugar-beep]

@DammyAji resolve conflicts please.

[DammyAji]

hey @snowrugar-beep please check now

[snowrugar-beep]

LGTM