perf(frontend): prevent unnecessary rerenders in stream timelines and charts

[arisu6804]

Problem

Per-tick updates can rerender every stream and chart, causing jank and battery use for accounts with many streams.

Objective

Deliver a production-quality improvement to stream lists, timelines, and chart rendering that creates measurable value for correctness, security, reliability, performance, or maintainability.

Implementation scope

• Memoize stable rows; isolate live tick state; virtualize or cap long lists; measure render and memory budgets.

Acceptance criteria

• Only affected live elements rerender; large lists meet a documented interaction budget; terminal streams stop updating.

Required validation

• Render-count tests, virtualized-list tests, fake-clock updates, and performance profiling checks.
• Existing tests and CI remain passing.
• Add regression coverage for the original failure mode.
• Do not weaken, delete, or skip unrelated tests to obtain a green build.

PR quality bar

• Keep the PR focused and explain design tradeoffs, compatibility impact, and test evidence.
• Avoid typo-only, documentation-only, cosmetic-only, or unrelated refactor submissions.

Out of scope

• Broad rewrites not required by the acceptance criteria.
• Changes to unrelated services, contracts, or user flows.