fix(ci): install uv via official script, not astral-sh/setup-uv action

The Gitea runner can't reliably resolve the astral-sh/setup-uv@v5 action — the
"Set up uv" step failed (exit 1) in build-images.yml (and the same step exists in
ci.yml). Replace the action with uv's official standalone install script
(`curl -LsSf https://astral.sh/uv/install.sh | sh`) + add $HOME/.local/bin to
$GITHUB_PATH, matching how the rest of the pipeline provisions tools (apt, corepack).
No third-party action dependency. Verified the install method yields a working uv on
a clean HOME. Same fix in both workflows.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

.gitea/workflows/build-images.yml

@@ -44,7 +44,12 @@ jobs:
         run: pnpm install --frozen-lockfile
 
       - name: Set up uv (for @parking/vision checks)
-        uses: astral-sh/setup-uv@v5
+        # Install uv via its official standalone script rather than a third-party action —
+        # the Gitea runner can't reliably resolve astral-sh/setup-uv. uv provisions the
+        # pinned Python (apps/vision/.python-version) itself. Add it to PATH for later steps.
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
 
       - name: Sync vision deps
         working-directory: apps/vision