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.

.readthedocs.yml

@@ -0,0 +1,13 @@
+version: 2
+
+build:
+  os: ubuntu-24.04
+  tools:
+    python: "3.13"
+
+sphinx:
+  configuration: docs/conf.py
+
+python:
+   install:
+   - requirements: docs/requirements-docs.txt