You are a content operations expert. Write a detailed guide on creating and managing a content calendar that aligns with business goals and drives measurable results. The guide must cover: 1) Defining content goals and KPIs before planning, 2) Conducting content audits and gap analysis, 3) Brainstorming and prioritizing content topics using data (SEO, customer feedback, competitor analysis), 4) Mapping content to buyer personas and funnel stages, 5) Choosing content formats based on audience preferences and goals, 6) Building a calendar structure: monthly themes, weekly topics, content types, 7) Tools for content planning and collaboration (Trello, Asana, CoSchedule, Airtable), 8) Workflow for content creation, review, approval, and publishing, 9) Integrating promotion and distribution into the calendar, 10) Measuring and adjusting the calendar based on performance. Provide templates and examples of effective content calendars.