fix: advance delivery indicator past Sent and add distinct double-tick

[MasterK0927]

The notify_message_delivery zome input uses serde rename_all=camelCase, so it expects messageRecord, but the client sent message_record. The payload failed to deserialize, the call threw, delivery acks were never recorded, and the indicator was stuck on a single tick. Send messageRecord to match.

Also render a dedicated double-check glyph for delivered messages instead of overlapping two single checks.

Summary

TODO:

• CHANGELOG updated

[Copilot]

Pull request overview

Fixes delivery-ack payload deserialization by aligning the UI payload shape with the backend’s serde(rename_all = "camelCase") expectations, and improves the UI delivery indicator by using a dedicated double-check glyph.

Changes:

• Send messageRecord (camelCase) instead of message_record when calling notify_message_delivery, so acks can be recorded and delivery status can advance beyond “Sent”.
• Update the delivery status UI to render a single icon that switches between checkMark and doubleCheck.
• Add a new doubleCheck SVG icon asset.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
ui/src/store/ConversationMessageStore.ts	Updates zome call payload key to messageRecord so delivery notifications deserialize correctly.
ui/src/routes/conversations/[id]/DeliveryStatusIndicator.svelte	Switches from overlapping two checkmarks to selecting a single icon (checkMark / doubleCheck) and adjusts sizing/spacing.
ui/src/lib/types.ts	Renames NotifyMessageDeliveryInput field to messageRecord to match the backend payload shape.
ui/src/lib/svgIcons.ts	Adds a doubleCheck SVG icon for delivered states.

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[Amirhesp]

@MasterK0927 Thanks for the PR. Could you please create a dev releas(v0.12.7-dev) to test the message delivery feature and also check that the synchronization is intact?