## Implementation Plan: Fix Avatar `size` Parameter

### Changes Required

**1. `devplacepy/avatar.py` — `generate_avatar_svg` function**

- Add a `size: int = 128` parameter (default preserves existing callers).
- After the SVG string is built (via `multiavatar(seed, None, None)`), inject `width="{size}"` and `height="{size}"` attributes into the root `<svg>` element. Use string manipulation (e.g., regex or `xml.etree.ElementTree`) to insert or replace the attributes. Keep the existing `viewBox` unchanged.
- Return the modified SVG.

**2. `devplacepy/routers/avatar.py` — avatar endpoint**

- Update the route function signature: `async def avatar_image(request: Request, seed: str, size: int = 128)`.
- Add size clamping: `size = max(16, min(512, size))`.
- Change the cache key from `seed` to `f"{seed}:{size}"`.
- Pass `size` to `generate_avatar_svg(seed, size=size)`.

**3. `tests/api/avatar.py` — add size-attribute test**

- Add a new test function:
  - Fetch `GET /avatar/multiavatar/test?size=32`, parse SVG, assert `width="32"` and `height="32"`.
  - Fetch `GET /avatar/multiavatar/test?size=256`, assert `width="256"`.
  - Optionally fetch without size parameter to verify default (128).
- Keep existing test(s) unchanged.

**4. Do not change any other files** — the CSS and JS masks are client-side and irrelevant to this fix; the devRant compatibility route is a reference only and must not be touched.

### Verification Steps

- Run `pip install -e '.[dev]' -q && make test-unit` — must exit 0, no new failures.
- Run `pip install -q ruff && ruff check .` — must exit 0.
- Confirm no new `ModuleNotFoundError` or side-effect test failures.

### Definition of Done

- [ ] `generate_avatar_svg` accepts `size` and returns SVG with explicit `width`/`height` matching that size.
- [ ] `avatar_image` router uses `size` in cache key, clamps input, and passes size to generator.
- [ ] Test exists that verifies `?size=32` returns SVG `width="32"` and `?size=256` returns `width="256"`.
- [ ] All existing unit tests pass (exit code 0).
- [ ] Ruff lint passes (exit code 0).
- [ ] No changes outside the three files listed above.