chore: sane ignore files, update summary, bump base images

- Add .claude/ to .gitignore and untrack settings.local.json
- Create .dockerignore to exclude docs, extension, analysis, scripts,
  node_modules, and other noise from the Docker build context
- Dockerfile: Node 20→22-alpine, Python 3.11→3.13-slim, DEBIAN_FRONTEND
  set, pip upgrade before install
- Track frontend/package-lock.json for reproducible builds
- Update summary.md: date, db.py in project structure, superseded column
  in schema, two new key patterns (12/13), full 2026-03-19 changelog

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

Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: Build frontend
-FROM node:20-alpine AS frontend-build
+FROM node:22-alpine AS frontend-build
 
 WORKDIR /frontend
 COPY frontend/package*.json ./
@@ -8,20 +8,22 @@ COPY frontend/ .
 RUN npm run build
 
 # Stage 2: Python backend with frontend static files
-FROM python:3.11-slim
+FROM python:3.13-slim
 
 WORKDIR /app
 
 # Install system dependencies
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    gcc \
-    libpq-dev \
-    gosu \
+RUN DEBIAN_FRONTEND=noninteractive apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+        gcc \
+        libpq-dev \
+        gosu \
     && rm -rf /var/lib/apt/lists/*
 
 # Install Python dependencies
 COPY backend/requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+RUN pip install --upgrade pip \
+    && pip install --no-cache-dir -r requirements.txt
 
 # Copy backend application
 COPY backend/ .