chore(assets): prune unused assets with unresolved provenance (#11735)

Merged via /merge-batch (v3.8.51 provenance sweep). Boarded and validated together with the batch's other provenance/asset-cleanup PRs in a combined worktree (typecheck:core, lint red-discriminator vs the pure release tip, complexity/cognitive-complexity ratchets, file-size, changelog-integrity, and the full focused test suite for every touched area all green). Static-asset-only cleanup, no runtime code changes. Thank you for the careful provenance audit.

changelog.d/maintenance/11735-prune-unresolved-provider-assets.md

@@ -0,0 +1 @@
+- **chore(assets):** remove four unused provider assets whose redistribution provenance could not be verified while retaining the active Freebuff SVG ([#11735](https://github.com/diegosouzapw/OmniRoute/pull/11735))

public/providers/freebuff-dark.svg

@@ -1,7 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
-  <rect width="100" height="100" rx="22" fill="#000000"/>
-  <!-- Sparkle in upper-left -->
-  <path d="M 36 16 C 36 28 26 38 14 38 C 26 38 36 48 36 60 C 36 48 46 38 58 38 C 46 38 36 28 36 16 Z" fill="#FFFFFF"/>
-  <!-- Terminal cursor bar -->
-  <rect x="44" y="46" width="34" height="14" rx="3" fill="#FFFFFF"/>
-</svg>

public/providers/freebuff-light.svg

@@ -1,7 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
-  <rect width="100" height="100" rx="22" fill="#000000"/>
-  <!-- Sparkle in upper-left -->
-  <path d="M 36 16 C 36 28 26 38 14 38 C 26 38 36 48 36 60 C 36 48 46 38 58 38 C 46 38 36 28 36 16 Z" fill="#FFFFFF"/>
-  <!-- Terminal cursor bar -->
-  <rect x="44" y="46" width="34" height="14" rx="3" fill="#FFFFFF"/>
-</svg>

public/providers/openvecta.svg

@@ -1,12 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" width="64" height="64" role="img" aria-label="OpenVecta">
-  <title>OpenVecta</title>
-  <defs>
-    <linearGradient id="ov-grad" x1="0" y1="0" x2="1" y2="1">
-      <stop offset="0%" stop-color="#7C3AED" />
-      <stop offset="100%" stop-color="#A855F7" />
-    </linearGradient>
-  </defs>
-  <rect x="2" y="2" width="60" height="60" rx="14" fill="url(#ov-grad)" />
-  <path d="M14 18 L32 46 L50 18" fill="none" stroke="#FFFFFF" stroke-width="6" stroke-linecap="round" stroke-linejoin="round" />
-  <circle cx="32" cy="40" r="3.5" fill="#FFFFFF" />
-</svg>