[lidarbtc]

Prefill the nickname field with the contact's profile name when no nickname is set, so it can be edited without retyping it. Existing nicknames still take priority, and contacts without either name keep an empty field.

Closes #309.

Screenshots

Before	After

Testing

pnpm ready passed on Ubuntu 26.04.1 with Node 24.12.0 and pnpm 10.28.1, including the dependency deduplication check, full build, lint, and all 963 existing tests.

Checked the dialog in Electron 40 under Xvfb using a temporary account and two synthetic contacts. The profile name appeared on first opening, saved nicknames took priority, and cancelling edits left the stored name unchanged. Saving updated the conversation name; removing the nickname restored the profile name. Clearing the field or opening a contact without either name left Save disabled.

No new tests were added.

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[lidarbtc]

@Bilb Since this is a feature PR, feel free to close it if you don't think it fits here.