Initial commit: snapshot of spesmilo/electrumx 2.0.0

Unmodified source tree of upstream commit 280cb339aa158e099eb936033eecd15719770651
("Merge pull request #389 from SomberNight/202607_release_2_0",
https://github.com/spesmilo/electrumx, release 2.0.0, 3 July 2026).

All Palladium-specific changes are in the commits that follow.

contrib/sdist/README.md

@@ -0,0 +1,29 @@
+# Source tarballs
+
+✓ _These tarballs should be reproducible, meaning you should be able to generate
+   distributables that match the official releases._
+
+This assumes an Ubuntu (x86_64) host, but it should not be too hard to adapt to another
+similar system.
+
+
+## Build steps
+
+1. Install Docker
+
+    See [`docker_notes.md`](https://github.com/spesmilo/electrum/blob/master/contrib/docker_notes.md).
+
+    (worth reading even if you already have docker)
+
+2. Build tarball
+
+    ```
+    $ ./contrib/sdist/build.sh
+    ```
+    If you want reproducibility, try instead e.g.:
+    ```
+    $ ELECBUILD_COMMIT=HEAD ELECBUILD_NOCACHE=1 ./contrib/sdist/build.sh
+    ```
+
+3. The generated distributables are in `./dist`.
+