Add chart line styling and table column alignment options

[TanayBensuYurtturk]

Adds per-series line styling to line/area/combo charts — curve, dash pattern, and colour, each with a chart-wide default plus a start-Y-at-zero toggle — and a per-column text alignment option for tables. Wired through the model, JSON schema, validator, TS types, and the renderer, with docs, skill updates, and an example dashboard.

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
pkg/dashboard/model.go:215
**Table alignment is never applied**

When a table column specifies `align`, YAML dashboards carry the value to the frontend but `TableWidget` ignores it, while JavaScript dashboard loading drops it entirely, causing headers and cells to retain their inferred alignment instead of the configured override.

### Issue 2
frontend/src/components/widgets/ChartWidget.tsx:1113-1116
**Combo styling bypasses new options**

When a combo chart configures `beginAtZero`, curve, dash, or color options, its separate rendering branch does not use these helpers or `yDomain`, causing the chart to remain auto-scaled with monotone, solid, palette-colored series.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "Add chart line styling and table column ..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "Apply curve/dash/color/zero to combo cha..." | Re-trigger Greptile}

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
pkg/dashboard/model.go:215
**TSX loader drops table alignment**

When a TSX/JSX dashboard configures a table column with `align`, `asTableColumns` constructs the model without copying that property, causing the server to omit it and the frontend to use inferred alignment instead.

### Issue 2
frontend/src/components/widgets/ChartWidget.tsx:1413-1415
**Combo lines ignore marker settings**

When a sparse combo chart omits `y.markers` or explicitly enables it, this line hardcodes markers off instead of using the shared density-aware marker logic, causing all combo line points to remain hidden.

```suggestion
                  strokeWidth={1.5}
                  dot={dotFor(rows.length)}
                  isAnimationActive={false}
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (3): Last reviewed commit: "Group per-series chart style under y.ser..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (4): Last reviewed commit: "Honor markers on combo lines; carry alig..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (5): Last reviewed commit: "Carry per-series line style inline on y...." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (6): Last reviewed commit: "gofmt model.go" | Re-trigger Greptile}

[greptile-apps]

_{Reviews (7): Last reviewed commit: "Show chart-wide curve/dash plus inline o..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (8): Last reviewed commit: "Show grouped per-series overrides in the..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (9): Last reviewed commit: "Add per-series line styling via a widget..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (10): Last reviewed commit: "Add per-series line styling via a widget..." | Re-trigger Greptile}