fix(brand): ship favicon.zip from #1235 (correct shield-with-cross mark)

[rumblefrog]

Summary

#1251 closed #1235 with a hand-authored "S" rounded-square SVG that mimicked .sidebar__brand-mark — but rumblefrog had attached the actual intended favicon set as a comment on the issue (favicon.zip). The shipped icon was therefore wrong on the dimension that mattered: stylistic riff on the sidebar brand, not the canonical SourceBans++ shield-with-cross mark (orange shield, black + centred, small white ++ tucked in the bottom-right — the literal "++" in SourceBans++).

This PR is two paired commits:

Commit 1 — fix(brand): ship favicon.zip from #1235 (correct shield-with-cross mark)

Replaces the icon artwork byte-faithful from the favicon.zip and adds the manifest plumbing the zip ships:

Asset	Before (#1251)	After (this PR)
favicon.svg	hand-authored S rounded-square w/ prefers-color-scheme: dark rule	shield-with-cross from zip
favicon.ico (theme + install)	2-icon (32 + 16)	3-icon (48 + 32 + 16) from zip
apple-touch-icon-180.png	hand-painted 180×180	from zip's apple-touch-icon.png (also 180×180); kept the existing filename so header.tpl's <link> doesn't move
favicon-96x96.png	—	new from zip; higher-DPI tab strips that pick a 96 source over the SVG
web-app-manifest-{192,512}x{192,512}.png	—	new from zip; maskable PWA install sources
site.webmanifest	—	new from zip; wires up the install-as-PWA path on Edge/Chrome

web/themes/default/core/header.tpl picks up two new <link> tags (<link rel="icon" sizes="96x96">, <link rel="manifest">) and the explanatory comment is refreshed to describe the new mark + manifest plumbing. The theme-color metas + the SVG / ICO / apple-touch-icon <link> tags from #1251 are unchanged — that scaffolding was correct; only the asset behind it was wrong.

The legacy installer (web/install/template/header.php) needs no markup change — it already references favicon.svg from the theme and favicon.ico from install/images/, both of which now ship the new mark.

One deviation from byte-faithful

The zip's site.webmanifest ships icon paths with a leading slash (/web-app-manifest-192x192.png), which only resolves correctly when the panel is hosted at the document root. Every typical SourceBans deploy lives in a subdirectory, so the leading slash is dropped — paths now resolve relative to the manifest URL itself. Same effect on a root-mounted install, working fix on a subdir install. The manifest's name field is also normalised from "Sourcebans++" (the zip's casing — looks like a Real Favicon Generator default that lowercased the input) to "SourceBans++" (the canonical project capitalisation).

theme_color / background_color in the manifest are left at the zip's #ffffff — those only affect installed-PWA chrome, which is a niche use case for an admin panel; the in-browser <meta name="theme-color"> tags continue to provide the brand-orange (#ea580c) light + zinc-950 (#09090b) dark treatment unchanged.

Commit 2 — fix(brand): wire template.logo setting back into the chrome brand mark

The template.logo admin setting (Admin → Settings → General → Logo path) was a vestigial v1.x setting in v2.0 — the legacy panel rendered it as a top-banner <img src="$logo">, and when the v2.0 chrome rewrote the layout to use .sidebar__brand-mark (a CSS-rendered "S" rounded-square), no template was updated to consume $logo anymore. The setting still appeared in the admin UI and saved back to a row nobody read; the default value (logos/sb-large.png) pointed at a path that didn't even exist in web/themes/default/.

Without this commit, the favicon swap above creates visual inconsistency: tab shows the new shield, sidebar / sign-in card / updater header show the old "S" / "SB". This commit resurrects the setting and wires it into the three brand-mark surfaces:

• core/navbar.tpl — the sidebar's top-left mark on every authenticated route. Renders <img src="{$theme_url}/{$logo}" …>. No View binds to this template (it's rendered procedurally by core/navbar.php), so SmartyTemplateRule doesn't fire — and $logo is in scope via core/header.php's assign (header runs before navbar in the page-builder lifecycle).
• page_login.tpl — the sign-in card's brand row. Same swap, but the template binds to Sbpp\View\LoginView so SmartyTemplateRule cross-checks property↔reference parity. Pre-resolves the joined URL in page.login.php and passes a single $brand_logo_url property (cleaner than threading both $theme_url + $logo through the View surface for what's just a precomputed themes/<theme>/<path>).
• updater.tpl — the DB updater's header. The updater bootstraps in its own context (web/updater/index.php) which doesn't load core/header.php, so $logo / $theme_url aren't in scope. Hardcoded to ../themes/default/images/favicon.svg here — the updater is an internal one-off page (admin-only, runs once per upgrade), and threading the setting through UpdaterView would be plumbing for zero customisation value.

Default value flips from the broken-in-v2.0 logos/sb-large.png to images/favicon.svg:

• web/install/includes/sql/data.sql — fresh installs.
• web/updater/data/808.php (registered in store.json) — paired migration converts existing installs whose value is still the v1.x default forward to the new default. Conditional WHERE means admins with custom values are untouched. Idempotent (the WHERE matches zero rows on re-run).

CSS: .sidebar__brand-mark rule drops the orange-rounded-square + centered-letter styling (background, color, display: grid; place-items: center, font-*, border-radius) that was designed for the pre-#1235 <div>S</div> shape. The new mark's visual identity (orange shield + cross) lives in the SVG itself; the CSS keeps just sizing + flex-shrink so the brand row's layout is unchanged.

Settings UI: adds a <p class="settings-fieldset__help"> below the "Logo path" input + aria-describedby link. Same shape as the sibling token-lifetime help paragraphs.

Closes #1235

Test plan

Favicon set (commit 1)

• Hard-refresh any panel page → tab favicon shows the orange shield-with-cross mark, not the plain orange "S".
• Devtools → Application → Manifest → manifest loads, both maskable icons resolve, no 404s on web-app-manifest-{192,512}x{192,512}.png.
• Devtools → Network → confirm favicon-96x96.png is requested by Chrome on a high-DPI display.
• Add the panel to an iOS home screen → the apple-touch-icon shows the new shield-with-cross mark.
• Light OS theme: in-browser chrome paints #ea580c. Dark OS: #09090b. (HTML metas; manifest's #ffffff doesn't apply in browser mode.)
• Visit web/install/ → the wizard's tab favicon shows the new shield-with-cross mark too (same .ico + the SVG <link> to the theme).
• Subdir install (e.g. served at /sourcebans/): manifest icons resolve relative to the manifest URL, not 404 against the document root.

Brand mark wire-up (commit 2)

• Sidebar top-left mark on every authenticated route (home, banlist, admin, …) shows the orange shield SVG, not the "S" letterform.
• ?p=login → sign-in card's brand row shows the orange shield SVG, not the "S" letterform.
• web/updater/ → the updater header shows the orange shield SVG, not the "SB" letterform.
• Admin → Settings → General → "Logo path" shows the new help text + aria-describedby is set on the input.
• Change template.logo to a custom path (e.g. images/favicon-96x96.png) → the sidebar / sign-in card immediately render the new asset on next page load. Restore default → reverts.
• Fresh install: template.logo is seeded as images/favicon.svg.
• Upgraded install whose template.logo was the v1.x default logos/sb-large.png: the 808.php migration converts it forward to images/favicon.svg. Admins who customised the value see no change.
• Re-running the updater on an already-converged install: 808.php no-ops (zero rows match the WHERE).