merge: upstream cinny v4.12.7 into lotus

Brings the 4.12.7 fixes: "%" sign wrapping below the composer input and
emoji autocompletion overwriting the preceding element. The release's
security half (sanitize-html, react-router-dom) was already applied in
91def3ad (we are on newer versions than upstream ships).

Resolved: kept our package.json/lockfile (the fork is ahead on every
dependency — React 19, router 7, i18next 26…), version 4.12.7-lotus, our
README/CONTRIBUTING, our "Lotus Chat vN" branding via pkg.version, and
the deleted GitHub-only workflows stay deleted. Note upstream announces
it is replacing matrix-js-sdk with its own SDK and pausing PRs; future
syncs will get harder.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

.github/DISCUSSION_TEMPLATE/issue-triage.yml

@@ -57,7 +57,7 @@ body:
       required: true
   - type: textarea
     attributes:
-      label: Environement
+      label: Environment
       description: |
         Please provide information about your environment. Include the following:
         - OS:

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,9 @@
+### Description
+
+<!-- Please include a summary of the change. -->
+
+Fixes #
+
+### Checklist:
+
+- [ ] I have read and understood the [Contribution policy](https://github.com/ajbura/cinny/blob/dev/CONTRIBUTING.md).