fix: render favicons from self-contained PNG and ICO assets

[ShenzheZhu]

The declared SVG favicon references an external PNG. Browsers omit that dependency when the SVG is used as an image, leaving a white tile even though the request succeeds. Use the existing self-contained PNG/ICO in Writer and Publisher metadata, and remove the unused SVG files and dedicated SVG routing entry.

Refs WriteHumanly/humanly-cloud#2401. Product artwork and page layout are unchanged. Five files, 13 removed lines; no dependencies or backend changes.

Validation:

• All favicon consumers traced; no remaining icon.svg references in packages. git diff --check passed.
• CI run 36012443713 passed: lint, script audit, both editions' type checks, runnable tests, complete package builds, and Docker smoke builds. CodeQL and Dependency Review also passed.
• Isolated frontend image built from the retained currently deployed no-pricing source plus only this patch. Browser checks passed for homepage, login, research/article pages, direct arXiv PDF links, Pricing 404 and no Pricing navigation links. PNG 96×96 and ICO 64×64 decode with visible pencil pixels; no SVG declarations remain.
• Mobile390px menu recheck passed after waiting for the client click handler: one click opens the visible dialog, no Pricing links, no horizontal overflow, no page JavaScript errors. Before/after screenshots inspected. The initial DOMContentLoaded-only check clicked before hydration on the slow tunnel; the corrected readiness check passed without product changes.
• OCR delegation and Ponytail review: Git total 5, reviewed 5, skipped 0, coverage 100%, no findings. Both deleted SVG files excluded by OCR were manually reviewed.

This source PR does not promote current Community main to the frozen managed deployment. The prepared managed image applies only these favicon changes to the retained live source; existing Pricing removal and research links remain. Provider-specific release details are retained in the private Cloud issue.

The reported Google search result is separate: Chrome decoded an inline 28×28 PNG whose pixels already depict a broken-image symbol. The original Google crawl/transform is unknown. This patch fixes the independently reproduced SVG defect and does not promise an immediate search-result refresh. No search-platform account changes were made.

Production release (2026-09-24)

Owner approved merging and deploying after acceptance and review. PR #8 merged as 526ba5e21e7a6cfec27eb30b34a708b0893e58be; the ready-for-review CI rerun 36018448728 also passed, along with CodeQL and Dependency Review.

The approved favicon patch is deployed to writehumanly.net using the existing managed production source. Production browser checks passed for homepage, login, research and article pages on desktop and mobile. PNG/ICO visibly decode with no SVG metadata; the mobile menu opens after hydration; there are no Pricing links and /pricing returns 404; both direct arXiv PDF links remain. No observed page JavaScript errors or horizontal overflow at 390px. Only the intended frontend container changed; the other six retain their prior IDs and images and all configured health checks are healthy.

The exact reported Google query still serves the pre-existing inline bitmap depicting a broken-image symbol. The website release is verified; Google search-result refresh is separate and has not yet been observed.