Remove command-center page and dependencies

The /admin/command-center route was platform_admin-only, used a heavy
custom theme (Major Mono / JetBrains / Inter Tight + ~700 lines of
schematic CSS), called three RPCs, and overlapped with the per-brand
dashboards reachable at /admin, /admin/orders, /admin/stops, and
/admin/reports. The page is being removed; it didn't justify the
build complexity, font payload, or schema surface area.

Changes:
- Drop page, dashboard component, CSS, and server actions
- Remove the platform_admin nav entry from header + sidebar
- Remove the cmd+K palette entry
- Add migration 0042 to drop the 3 RPCs, founder_pain_log table,
  and founder_pain_log_platform view it owned
- Decrement route count in docs/pricing-assessment.md (88 -> 87)

Verification: tsc clean, eslint clean, npm run build clean, command-
center absent from the route list.

db/migrations/0042_drop_command_center.sql

@@ -0,0 +1,19 @@
+-- Migration 0042: Drop command-center RPCs and founder_pain_log
+--
+-- The /admin/command-center page is being removed (see commit message).
+-- All objects it depended on are also dropped:
+--   - get_platform_command_center_metrics (JSONB-returning RPC)
+--   - get_platform_activity_feed          (TABLE-returning RPC)
+--   - get_brand_health_snapshot           (TABLE-returning RPC)
+--   - founder_pain_log                    (table)
+--   - founder_pain_log_platform           (view, joins brand name onto founder_pain_log)
+--
+-- The platform_admin role has no other consumer of these objects. The
+-- cross-brand KPIs and activity feed that the page showed are reachable
+-- per-brand via /admin, /admin/orders, /admin/stops, and /admin/reports.
+
+DROP VIEW IF EXISTS founder_pain_log_platform;
+DROP FUNCTION IF EXISTS get_brand_health_snapshot();
+DROP FUNCTION IF EXISTS get_platform_activity_feed();
+DROP FUNCTION IF EXISTS get_platform_command_center_metrics();
+DROP TABLE IF EXISTS founder_pain_log;