Foundation: route, recharts, sprint-dates migration, chart-colors helper (#46)

* feat(ST-1201): add Sprint start_date/end_date + claude_jobs index migration

- Sprint model: optionele start_date en end_date (DATE) voor burndown x-as
- CREATE INDEX claude_jobs(status, finished_at) voor agent-throughput-queries
- Bestaande sprints houden NULL; burndown skipt die

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

* feat(ST-1202): add lib/chart-colors.ts + vitest coverage

MD3-token-to-CSS-var mappings for STATUS, PRIORITY, VERIFY, JOB_STATUS
and SERIES_COLORS; all 5 tests pass.

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

* feat(ST-1203): add Insights link to NavBar

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

* feat(ST-1204): move Insights NavBar link between Solo and Todo's

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

* feat(ST-1205): add sprint start_date/end_date UI + server actions

- createSprintAction + updateSprintDatesAction: Zod date validation
  with end_date >= start_date cross-check
- start-sprint-button: date inputs in create dialog
- sprint-header: date display button + edit dialog with updateSprintDatesAction
- sprint page: select start_date/end_date for SprintHeader prop
- Demo blokkade via bestaande isDemo checks
- 6 tests groen (validation + demo guard)

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

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/chart-colors.ts

@@ -0,0 +1,39 @@
+// Mapping van MD3-tokens naar CSS-var-strings voor Recharts fill/stroke.
+// Recharts accepteert gewone strings — 'var(--status-done)' werkt direct.
+export const STATUS_COLORS = {
+  TO_DO: 'var(--status-todo)',
+  IN_PROGRESS: 'var(--status-in-progress)',
+  REVIEW: 'var(--status-in-progress)',
+  DONE: 'var(--status-done)',
+} as const
+
+export const PRIORITY_COLORS = {
+  1: 'var(--priority-critical)',
+  2: 'var(--priority-high)',
+  3: 'var(--priority-medium)',
+  4: 'var(--priority-low)',
+} as const
+
+export const VERIFY_COLORS = {
+  ALIGNED: 'var(--status-done)',
+  PARTIAL: 'var(--priority-medium)',
+  EMPTY: 'var(--priority-critical)',
+  DIVERGENT: 'var(--priority-high)',
+} as const
+
+export const JOB_STATUS_COLORS = {
+  queued: 'var(--muted-foreground)',
+  claimed: 'var(--status-in-progress)',
+  running: 'var(--status-in-progress)',
+  done: 'var(--status-done)',
+  failed: 'var(--priority-critical)',
+  cancelled: 'var(--muted-foreground)',
+} as const
+
+export const SERIES_COLORS = [
+  'var(--chart-1)',
+  'var(--chart-2)',
+  'var(--chart-3)',
+  'var(--chart-4)',
+  'var(--chart-5)',
+] as const