Migrate to PostgreSQL + add FastAPI webapp for Coolify deploy

Backend migration:
- Replace pyodbc/SQL Server with psycopg2/PostgreSQL throughout
- Rewrite Database class with portable SQL: SERIAL, ON CONFLICT, NOW()
- Lowercase table names (rip_help_files, rip_help_sections) - Postgres convention
- libpq connection string format in HELP_DB_CONN

Webapp (webapp/):
- FastAPI app: GET /, GET /images/<f>, GET /home-image, GET /api/sections,
  POST /api/keywords/<code>, GET /healthz
- Jinja2 template extracted from generate_html.py with HTTP image URLs
- Direct keyword save to DB (no JSON download detour)
- Same prefix scoping as CLI tools (?prefix=RIP)

Deployment:
- Dockerfile (python:3.12-slim + uvicorn)
- docker-compose.yml for local dev
- requirements-webapp.txt (minimal, no Windows-only deps)
- .dockerignore excludes pipeline scripts and BAT files
- README updated with webapp section and Coolify deploy guide

Also: switch AI model to claude-haiku-4-5 (~3x cheaper, same quality for this task)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,19 @@
+# Slim Python image; psycopg2-binary включва свои libs, не е нужен build deps
+FROM python:3.12-slim
+
+WORKDIR /app
+
+# Сваляме само файловете нужни за webapp-а (не и Windows-only deps)
+# Затова инсталираме отделен webapp-requirements без pywin32 / pdfplumber / docx
+COPY requirements-webapp.txt /app/
+RUN pip install --no-cache-dir -r requirements-webapp.txt
+
+# Кода
+COPY webapp /app/webapp
+
+# Изходна директория за картинките — Docker volume mount
+ENV OUTPUT_DIR=/data/help_output
+
+EXPOSE 8000
+
+CMD ["uvicorn", "webapp.main:app", "--host", "0.0.0.0", "--port", "8000", "--proxy-headers", "--forwarded-allow-ips=*"]