Feature/multi contract indexer

[nonso7]

Closes #352

[ogazboiz]

The contracts CI is failing on the rustfmt format check. This isn't a logic issue, just formatting.

Run this in the contracts directory and push:

cd contracts
cargo fmt

Then commit and push the formatting changes. The CI should pass after that.

[ogazboiz]

hey @nonso7, same as #527, this diff is over 20,000 lines. please break it into smaller PRs so we can review properly.

also no CI ran on this branch. push a small commit to trigger it after splitting.

[ogazboiz]

The codebase issues on main have been resolved and all CI checks are passing now. Please rebase your branch to pull in the latest changes before continuing. Thanks for your patience.

[ogazboiz]

19k+ additions, mostly snapshots. Same migration conflict as #527 (both use 1779000000010). Committed error.txt and error_tests.txt build logs. Has merge conflicts. Clarify dependency relationship with #527 since they share identical backend changes.

[ogazboiz]

heads up, a few important changes just landed on main that affect your PR:

1. axios pinned to 1.13.5 - there's an active supply chain attack on axios 1.14.1 (pulls in confirmed malware). we added overrides in all package.json files to block it.

2. CI now runs a supply chain audit before backend/frontend jobs. if your lockfile has a compromised package, CI will fail with a clear error.

3. backend test fixes - loanEndpoints tests now use valid Stellar addresses and base64 strings. if your PR was failing backend CI but you didn't touch backend code, this should fix it after rebase.

please rebase on latest main:

git fetch upstream
git rebase upstream/main
git push --force-with-lease