docs: cache-bust PyPI badge URLs to refresh GitHub Camo

[ljagiello]

The PyPI badges in README.md still show "package or version not found" because GitHub Camo cached the SVG before `friday-agent-sdk 0.1.1` was published. Camo's natural TTL is 3h (`expires: 04:45:07 GMT` from initial cache at `01:45:07 GMT`), and `PURGE` requests against the camo URLs returned 200 but didn't actually invalidate.

This was supposed to be in #12 (commit `8305b5b`) but landed after the squash-merge.

What this does

Adds `?v=1` to the two PyPI badge URLs:

• Shields.io ignores unknown query strings, so the badge content is unchanged.
• The Camo URL hash is derived from the source URL, so a new query string ⇒ a new Camo URL ⇒ fresh fetch from shields.io ⇒ correct `v0.1.1` displayed.

The CI and License badges are untouched.

Test plan

• `vp check` clean
• After merge, hard-refresh the repo home page and confirm both PyPI badges show real values (`v0.1.1` and `3.12 | 3.13 | 3.14`).