feat(M1): Project scaffolding, DB schema, core infrastructure

- Initialize Rust workspace with 7 crates (pm-web, pm-worker, pm-core,
  pm-agent-client, pm-auth, pm-ca, pm-reports)
- React + TypeScript + Vite + MUI frontend scaffold
- Full PostgreSQL schema: all 17 tables with indexes and constraints
- pm-core: config (TOML+env), db (SQLx pool + migrations), error
  (unified AppError + JSON envelope), request_id (ULID middleware),
  logging (tracing JSON/pretty)
- pm-web: Axum skeleton, /status/health endpoint, static file serving
- pm-worker: Tokio skeleton, heartbeat writer, schema version check
- Embedded sqlx migrations with advisory lock (single-writer)
- systemd unit files, setup.sh, build-frontend.sh
- config.example.toml with all configuration keys
- docs/runbooks/restore.md
- cargo check passes with zero warnings

Closes M1.

frontend/src/theme/theme.ts

@@ -0,0 +1,23 @@
+import { createTheme } from '@mui/material/styles'
+
+export const lightTheme = createTheme({
+  palette: {
+    mode: 'light',
+    primary:   { main: '#1565C0' },
+    secondary: { main: '#0288D1' },
+  },
+  typography: {
+    fontFamily: '"Roboto", "Helvetica", "Arial", sans-serif',
+  },
+})
+
+export const darkTheme = createTheme({
+  palette: {
+    mode: 'dark',
+    primary:   { main: '#42A5F5' },
+    secondary: { main: '#26C6DA' },
+  },
+  typography: {
+    fontFamily: '"Roboto", "Helvetica", "Arial", sans-serif',
+  },
+})