fix(ci): generate stub files before flutter analyze

The generated/ directory (app_config.dart, theme_colors.dart) is created
by build_whitelabel.py from theme.json. Since theme.json is not in the
repo, the lint gate fails on missing generated imports.

Added ci_stub_gen.py to produce minimal stubs so flutter analyze passes
before the whitelabel build step. Wired into all jobs in ci.yml and
release.yml.

.gitea/workflows/release.yml

@@ -30,6 +30,10 @@ jobs:
       - name: Install dependencies
         run: flutter pub get
 
+      - name: Generate stubs (lint gate support)
+        if: hashFiles('theme.json') == ''
+        run: python3 ci_stub_gen.py
+
       - name: Analyze Dart code
         run: flutter analyze --fatal-warnings
 
@@ -55,6 +59,9 @@ jobs:
       - name: Install dependencies
         run: flutter pub get
 
+      - name: Generate stubs (lint gate support)
+        run: python3 ci_stub_gen.py
+
       - name: Run tests
         run: flutter test --reporter=expanded
 
@@ -101,6 +108,9 @@ jobs:
       - name: Install Flutter dependencies
         run: flutter pub get
 
+      - name: Generate stubs (lint gate support)
+        run: python3 ci_stub_gen.py
+
       # If release signing secrets are available, write keystore
       # and update build.gradle.kts to use a release signing config.
       # Otherwise fall back to debug keys (current state of the repo).