Fix NPM ECDSA CI: use committed yarn.lock instead of upgrading deps (#3863)

## Summary

- Fix the NPM ECDSA workflow that has been failing since October 2025
due to cross-dependency incompatibilities introduced by `yarn upgrade
--exact`
- Replace blind upgrade to latest `development`-tagged npm packages with
`yarn install --frozen-lockfile` to use committed yarn.lock with
known-compatible versions

## Root Cause

The `yarn upgrade --exact` step in `npm-ecdsa.yml` pulls the latest
`development`-tagged versions of
`@threshold-network/solidity-contracts`, `@keep-network/random-beacon`,
and `@keep-network/sortition-pools`. This creates a breaking
combination:

- `@threshold-network/solidity-contracts@1.3.0-dev.16` **removed**
`approveApplication()` from the TokenStaking contract source (compiled
ABI drops from 40+ to 35 methods)
- `@keep-network/random-beacon@2.1.0-dev.18` deploy script
`05_approve_random_beacon_in_token_staking.js` still **calls**
`execute("TokenStaking", ..., "approveApplication", ...)`

Result: `Error: No method named "approveApplication" on contract
deployed as "TokenStaking"`

## Verification

- Reproduced locally: `yarn upgrade --exact` + clean deploy → same
failure
- Confirmed with committed `yarn.lock` (`@1.3.0-dev.5` +
`@2.1.0-dev.13`): deploy succeeds
- This workflow was already failing on the previous run (2025-10-15) —
pre-existing, not caused by #3826

## Note on Client CI

The Client workflow failure is also pre-existing (confirmed by scheduled
run at `2026-02-12T01:43` before #3826 merge at `06:41`). Root causes
are infrastructure issues: expired ElectrumX TLS certificates (since
2023-04-01), Infura rate limiting, and a goroutine race condition in
`blockcounter.go`. Not addressed in this PR.

## Test plan

- [ ] NPM ECDSA workflow passes on merge to main
- [ ] Verify `yarn deploy:test --network hardhat --write true` succeeds
in CI with frozen lockfile

Author: lrsaturnino

.github/workflows/npm-ecdsa.yml

@@ -33,12 +33,8 @@ jobs:
           cache: "yarn"
           cache-dependency-path: solidity/ecdsa/yarn.lock
 
-      - name: Resolve latest contracts
-        run: |
-          yarn upgrade --exact \
-            @keep-network/random-beacon \
-            @keep-network/sortition-pools \
-            @threshold-network/solidity-contracts
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
 
       # Deploy contracts to a local network to generate deployment artifacts that
       # are required by dashboard and client compilation.