Bar chart with exact proportional heights for [4, 10, 6, 8, 12]

Draw a vertical bar chart in SVG for the five quarterly values below, using a 240x170 viewBox. Write the chart to `chart.svg`. Values (left to right): Q1 = 4, Q2 = 10, Q3 = 6, Q4 = 8, Q5 = 12. Requirements: - Use exactly five `<rect>` bars, one per quarter, in left-to-right order Q1, Q2, Q3, Q4, Q5. - Each bar's height must be proportional to its value, so the height ratios match the value ratios (the Q5 bar is the tallest, the Q1 bar the shortest). - All five bars sit on one shared horizontal baseline (their bottom edges align). - Add a `<text>` label under each bar reading Q1, Q2, Q3, Q4, Q5 respectively. - Vector primitives only: no raster images, no data: URIs, no base64, no <foreignObject>, no <script>, no external references. A baseline `<line>` is fine.