datasheet-lens MCP server

The store now keeps one part for each MPN and manufacturer. In 0.1.0, two
names of one manufacturer ("TI" and "Texas Instruments") made two parts
with the same MPN and the same datasheet.

- Manufacturer registry in the store. Two names are one manufacturer when
  they are equal with no case, punctuation or legal suffix ("Microchip" and
  "Microchip Inc."), or when the registry has them as aliases. The registry
  starts with the names of the built-in manufacturer table and the short
  names TI, ADI and ST. It does not follow the name changes and mergers of
  companies.
- New CLI command `maker` and MCP tool `manufacturer_relation`. They show
  the registry and the pairs of names to examine. They record two names as
  one manufacturer (`alias`) or as two manufacturers (`distinct`, a second
  source). After `alias`, the parts with the same MPN merge.
- A part with the MPN of a stored part and a manufacturer name that the
  registry does not relate stops with an error. The error gives the two
  commands. The store does not make a second part.
- A project part keeps the manufacturer name of the project: the layout
  uses it as a folder. The project tools compare the names through the
  registry.
- `stock` and `project_availability`: when one MPN has offers of two or
  more manufacturers (a second source), the tool uses only the offers of
  the manufacturer of the part. A Mouser part with the state "Restricted
  Availability" gets a WARNING: Mouser does not sell it now, and this is
  not the lifecycle state of the manufacturer. The lead time is in English
  ("182 days"). An empty lifecycle state is not shown as "unknown".
- The documentation and the Mouser error tell that the key must be the key
  of the Search API, not of the Cart API.
- Install from PyPI: `pipx install datasheet-lens`.

Upgrade:

- The first open of the store with 0.2.0 fills the registry. It merges the
  parts with the same MPN and the same manufacturer (for example "TI" and
  "Texas Instruments", or "Microchip" and "Microchip Technology Inc."),
  with their documents and saved facts. The store schema does not change:
  0.1.0 still opens the store.
- The formats of the index and of the element map do not change. No new
  build is necessary.
- Restart the MCP client after the upgrade.