Envelope budget: Budget page, per-month assignments stored on a Budget tab, rollover and ready-to-assign

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Dockerfile

@@ -6,7 +6,7 @@ WORKDIR /app
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
-COPY statement_loader.py seed_rules.py app.py app_page.html app_dashboard.html ./
+COPY statement_loader.py seed_rules.py budget.py app.py app_page.html app_dashboard.html app_budget.html ./
 COPY template/ ./template/
 
 # statements, Bills_Tracker.xlsx and backups live in this volume, never in the image