feat: bridgeController consume complete event

[infiniteflower]

Explanation

The bridge quote stream API emits a complete SSE event just before closing the stream. Previously this event was silently ignored by the client. This PR adds support for consuming it.

The complete event carries metadata about the stream result — how many quotes were sent, whether any quotes were available, an optional reason code (e.g. AMOUNT_TOO_LOW, TOKEN_NOT_SUPPORTED), and optional context. This information is useful for the UI to distinguish between "no quotes because the stream hasn't finished yet" vs "no quotes because the API determined there are none for this request".

Changes:

• Added QuoteStreamCompleteReason enum and QuoteStreamCompleteSchema / validateQuoteStreamComplete to validators.ts, following the same pattern as TokenFeatureType / validateTokenFeature.
• Added QuoteStreamCompleteData type (inferred from the schema) to types.ts.
• Added quoteStreamComplete: QuoteStreamCompleteData | null to BridgeControllerState, defaulting to null.
• quoteStreamComplete is cleared at the start of each fetch and in resetState, matching the behaviour of tokenWarnings.
• Added onComplete to the serverEventHandlers object in fetchBridgeQuoteStream, dispatched via a new case 'complete': branch in onMessage.
• The complete event does not set quotesLoadingStatus to FETCHED — that remains owned by onClose, which must first await any in-flight appendFeesToQuotes promises (L1 gas fee or snap fee calculations that may still be running when the stream closes).
• Exported QuoteStreamCompleteData, QuoteStreamCompleteReason, and validateQuoteStreamComplete from the package's public index.ts.

References

https://consensyssoftware.atlassian.net/browse/SWAPS-4224

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them