refactor(filters): mount-scope store bindings and fix effect-update loop

Replace the side-effect-on-import $effect.root in bindings with an explicit
startFilterBindings() started from an AppBindings provider in onMount, so the
filters/sort -> font-catalog bridge has a lifecycle tied to the app tree and a
returned cleanup. bindings now consumes getFontCatalog().

Fix the effect-update loop this surfaced: setGroups populated the reactive
groups array in place via `groups.length = 0; groups.push(...)`. push reads the
array's length signal, so the populating effect both read and wrote
groups.length each run and re-triggered itself forever
(effect_update_depth_exceeded). setGroups now reassigns the array (groups is
`let`), which does not read length.

Extract mapFilterMetadataToGroups to own the metadata -> group-config mapping,
including sorting a copy of options (the source is TanStack-cached data; an
in-place sort corrupts the cache and writes into the effect's read dependency).

src/app/providers/index.ts

@@ -1 +1,2 @@
+export { default as AppBindingsProvider } from './AppBindings.svelte';
 export { default as QueryProvider } from './QueryProvider.svelte';