Project skeleton #5

Goal

Set up the Python project (uv, Ruff, pytest), the SerpApi client with its cache and credit counter, the shared result models, and the Play Store adapter as the pattern everyone else copies.

Builds on

#2, #4

Done when

• uv sync, ruff and pytest pass on a fresh clone
• The client caches responses, counts searches, has an offline mode and never logs URLs
• The Play Store adapter works, with a scrubbed fixture and tests