fix: validate API key in PlaneHeaderAuthProvider and pin fakeredis<2.35.0 (#105)

* fix: validate API key against Plane API in PlaneHeaderAuthProvider

PlaneHeaderAuthProvider accepted any non-empty string as a valid API key
without verifying it against the Plane API. Now verify_token makes a
lightweight GET /api/v1/users/me/ call to confirm the key is valid before
granting access, matching the pattern used by PlaneOAuthTokenVerifier.

* fix: pin fakeredis<2.35.0 to avoid pydocket import error

pydocket 0.16.6 (transitively pinned by fastmcp==2.14.4) imports
`FakeConnection` from `fakeredis.aioredis`, which was removed in
fakeredis 2.35.0. This caused server startup to fail with:

  ImportError: cannot import name 'FakeConnection' from 'fakeredis.aioredis'

Pin fakeredis[lua] to >=2.32.1,<2.35.0 (matching pydocket's lower bound)
until fastmcp upgrades to a newer pydocket.

* fix: use x-api-key header for Plane API key validation

The Plane backend expects API keys in the `x-api-key` header, not as a
Bearer token in `Authorization`. Update the API key validation request
to match.

* chore: bump version - 0.2.9