fix(ci): fix YAML parse error in update-manifest step

Multi-line python3 -c "..." with zero-indented Python code caused Gitea
to fail parsing the workflow YAML (line 188: could not find expected ':').
Replace with jq which handles variable interpolation in a single line.

This was silently breaking every push-triggered workflow run.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -184,21 +184,13 @@ jobs:
           VERSION=$(echo "$RELEASE" | python3 -c "import sys,json; print(json.load(sys.stdin)['name'].split()[-1])")
           DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ)
 
-          python3 -c "
-import json, sys
-manifest = {
-    'version': '$VERSION',
-    'notes': 'Latest Lotus Chat release',
-    'pub_date': '$DATE',
-    'platforms': {
-        'windows-x86_64': {
-            'url': '$BASE/LotusChat-x86_64-setup.nsis.zip',
-            'signature': '''$WIN_SIG'''
-        }
-    }
-}
-print(json.dumps(manifest, indent=2))
-" > release.json
+          jq -n \
+            --arg version "$VERSION" \
+            --arg date "$DATE" \
+            --arg url "$BASE/LotusChat-x86_64-setup.nsis.zip" \
+            --arg sig "$WIN_SIG" \
+            '{"version":$version,"notes":"Latest Lotus Chat release","pub_date":$date,"platforms":{"windows-x86_64":{"url":$url,"signature":$sig}}}' \
+            > release.json
 
           cat release.json