Fix stale UI cache, BEN2 edge quality, and fresh-install permissions

- Serve /dist and /src with Cache-Control: no-cache so browsers always
  revalidate the webpack bundle (it has a fixed filename with no content
  hash, so a stale browser cache was hiding the new Remove Background
  model dropdown after the rebuild).
- Enable BEN2's refine_foreground pass by default - it's the model's own
  documented option for preserving fine/semi-transparent edge detail
  (text borders, light rays) instead of a harder cutout, at a small
  speed cost.
- Make install-local-gpu.sh and bring-up-local-gpu.sh pre-create ./data
  as the invoking non-root user before Docker ever runs, so its daemon
  never gets a chance to auto-create those bind-mount dirs as root.
- Make prefetch-models.sh self-heal a root-owned ./data automatically
  (sudo chown) instead of erroring out with a manual fix-it command.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ro4PwQKvSc3CH19LSN21Ht

install-local-gpu.sh

@@ -80,6 +80,18 @@ fi
 
 echo ""
 
+# ── 0.5. Pre-create ./data with correct ownership ────────────────────────────
+# Docker's daemon (always root) auto-creates bind-mount source directories on
+# the first 'compose up' if they don't exist yet — leaving ./data root-owned
+# and blocking the invoking user from later running ./prefetch-models.sh
+# without a manual 'sudo chown'. Create it now, owned by the real (non-root)
+# user, so that problem has no chance to happen on a fresh checkout.
+REPO_DIR="$(cd "$(dirname "$0")" && pwd)"
+mkdir -p "$REPO_DIR"/data/{models,hf_cache,projects,patches}
+chown -R "${SUDO_UID:-$(id -u)}:${SUDO_GID:-$(id -g)}" "$REPO_DIR/data"
+echo "✓ ./data prepared (writable without sudo)"
+echo ""
+
 # ── 1. NVIDIA container toolkit ──────────────────────────────────────────────
 if command -v nvidia-ctk &>/dev/null; then
     echo "✓ nvidia-container-toolkit already installed — skipping"