docs(citation): back-fill Zenodo concept + v1.0.1 DOIs

Zenodo minted the clean v1.0.1 release after the history rewrite.

  - concept DOI 10.5281/zenodo.20389794 (all versions; always resolves
    to the latest release) is now the primary identifier: CITATION.cff
    top-level doi, README badge, citation prose, and BibTeX.
  - version DOI 10.5281/zenodo.20438189 (v1.0.1 specifically) is listed
    in CITATION.cff identifiers for precision.
  - BibTeX cite-key de-versioned to geurten_digimuh so it stays stable
    across future releases.

The retired v1.0.0 DOI (10.5281/zenodo.20389795) is intentionally not
referenced anywhere; that record archived the private herd data and is
being removed on Zenodo.

Author: bgeurten

CITATION.cff

@@ -4,9 +4,17 @@ message: "If you use this software, please cite it as below."
 type: software
 version: "1.0.1"
 date-released: "2026-05-29"
+doi: "10.5281/zenodo.20389794"
 license: MIT
 repository-code: "https://github.com/zerotonin/digimuh"
 url: "https://zerotonin.github.io/digimuh/"
+identifiers:
+  - type: doi
+    value: "10.5281/zenodo.20389794"
+    description: "Concept DOI — always resolves to the latest DigiMuh release"
+  - type: doi
+    value: "10.5281/zenodo.20438189"
+    description: "Zenodo archive of DigiMuh v1.0.1"
 keywords:
   - dairy
   - cattle

README.md

@@ -6,6 +6,7 @@
 [![Python](https://img.shields.io/badge/python-3.10%20%7C%203.11%20%7C%203.12%20%7C%203.13-blue.svg)](https://www.python.org/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 [![Ruff](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/astral-sh/ruff/main/assets/badge/v2.json)](https://github.com/astral-sh/ruff)
+[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.20389794.svg)](https://doi.org/10.5281/zenodo.20389794)
 [![Uses reRandomStats](https://img.shields.io/badge/uses-reRandomStats%20v0.2.0-009E73.svg)](https://doi.org/10.5281/zenodo.20387255)
 
 **DigiMuh** consolidates ~8.9 GB of heterogeneous dairy-cow CSV sensor data into
@@ -209,15 +210,16 @@ and on the GitHub repo's *Cite this repository* button.
 
 > Geurten, B. R. H. (2026). *DigiMuh: Dairy-cow sensor data ingestion
 > and heat-stress analysis pipeline* (Version 1.0.1) [Software].
-> Zenodo. https://github.com/zerotonin/digimuh
+> Zenodo. https://doi.org/10.5281/zenodo.20389794
 
 ```bibtex
-@software{geurten_digimuh_v101,
+@software{geurten_digimuh,
   author  = {Geurten, Bart R. H.},
   title   = {{DigiMuh}: Dairy-cow sensor data ingestion and heat-stress
              analysis pipeline},
   year    = {2026},
   version = {1.0.1},
+  doi     = {10.5281/zenodo.20389794},
   url     = {https://github.com/zerotonin/digimuh},
   license = {MIT},
 }