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/ci.yml

@@ -35,9 +35,12 @@ jobs:
         # The vision service is a Python package wired into the Turbo graph via a
         # package.json shim; its lint/typecheck/test scripts shell to `uv run …`. CI
         # has no Python by default, so `uv run` would fail with "uv: not found" and
-        # break the whole Turbo run. uv provisions the pinned Python (.python-version)
-        # itself. See wiki/decisions/vision-service-packaging.md.
-        uses: astral-sh/setup-uv@v5
+        # break the whole Turbo run. Install uv via its official standalone script
+        # (the Gitea runner can't reliably resolve astral-sh/setup-uv); uv provisions the
+        # pinned Python (.python-version) itself. See wiki/decisions/vision-service-packaging.md.
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
 
       - name: Sync vision deps
         # Light deps + the dev group (ruff/mypy/pytest) only — NOT the optional `alpr`