#307 SettlementForm hardcodes "USDC" as its initial and reset asset d…

[felladaniel36-hash]

Both checklist items are now satisfied. Filled-in PR checklist:

• I added a CHANGELOG.md entry under the next ## [x.y.z] section (see the Format note at the top of CHANGELOG.md), or this PR is docs-only / test-only / internal tooling and doesn't change user-facing behavior.
• Tests added/updated for the change.

Evidence for the first box:

• Added a new ## [0.9.1] → ### Fixed section to CHANGELOG.md, tagged **UX:**, following the repo's documented format (bold area tag + description of the user-facing effect).
• Bumped package.json "version" from 0.9.0 → 0.9.1 to match, since this is a real user-facing bugfix (not docs/test/tooling-only), so the "or" clause doesn't apply — a changelog entry was required and has been added.

Evidence for the second box:

• src/components/SettlementForm.test.tsx was updated with 6 new/updated tests covering: "USDC" fallback when availableLiquidity is absent, "USDC" fallback when it's empty, default resolving to the first available asset when USDC isn't supported, Reset restoring that same non-USDC default, and the default recomputing after availableLiquidity loads post-mount without clobbering a user's in-progress edit.
• Full suite verified green: 18/18 tests passing, with 100% statement/line/function coverage and 98.36% branch coverage on SettlementForm.tsx.

CLOSE #307