fix(docs): commit the architecture diagrams that .gitignore swallowed

A blanket `*.png` rule meant the eight diagrams added alongside the
ARCHITECTURE.md rewrite were silently skipped — `git add` reported nothing and
the doc landed referencing images that were not in the repo. Every diagram
rendered as a broken image on GitHub.

Force-includes docs/images/ the same way docs/screenshots/ and the extension
cover icons already are, covering both the architecture diagrams and the
funding QR codes that follow.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -123,6 +123,13 @@ SECURITY_AND_CODE_AUDIT.md
 !/docs/screenshots/
 !/docs/screenshots/*.png
 
+# …and the hand-authored documentation diagrams (architecture) plus the locally
+# generated donation QR codes (funding). Both are referenced directly from
+# committed Markdown, so leaving them ignored publishes docs with broken images.
+!/docs/images/
+!/docs/images/architecture/*.png
+!/docs/images/funding/*.png
+
 # …and the bundled marketplace extension cover icons — real source assets
 # imported/hashed by Vite, so they must be committed.
 !/frontend/src/assets/extension-icons/