fix(web): render stored HEIC attachments

[Gigioxx]

Stored HEIC photos uploaded from another client render as broken images on Desktop. Upload-time conversion only helps newly attached files.

Reuse the existing HEIC decoder when native image decoding fails, through one shared component used by the timeline, composer thumbnails, and lightbox. Ordinary images stay on the native path. Converted preview URLs are released on unmount, and navigation discards unfinished conversions. Stored attachments remain unchanged.

Fixes #10356.

Verified 34 focused tests, web typecheck, scoped lint, and formatting. In Chromium against an isolated server, all eight stored HEIC images went from naturalWidth: 0 to 1280; lightbox navigation and a restored HEIC composer draft also rendered correctly. Web and Desktop share these components; the packaged Electron app was not rebuilt. Mobile and workspace-file previews are unchanged. React Doctor reports no compiler errors; its async-state/error-forwarding warnings remain on the cancellation-guarded fallback, whose stale-decode behavior is tested.

Timeline before	Timeline after

Model: GPT-6. Harness: Codex in T3 Code.

[macroscopeapp]

Approvability

Verdict: Would Approve

Macroscope's review found this PR approvable — This is a contained web bug fix that preserves native rendering for ordinary images and adds a tested, client-side fallback for previously broken stored HEIC previews. It does not change stored data, APIs, product defaults, deployment behavior, or sensitive functionality.

Not approved because:

• Monthly spending limit reached (workspace setting). Approvability relies on correctness review in order to determine eligibility

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