feat(portal-bff): observability foundations (Pino + CLS + OTel)

Implements ADR-0012 phase 1, BFF side. The SPA wiring is a
separate phase-2 PR.

Runtime libraries added (production deps):

- nestjs-pino, pino, pino-http   structured JSON logging
- nestjs-cls                     request-scoped context
- @opentelemetry/api / sdk-node / resources / semantic-conventions
- @opentelemetry/exporter-trace-otlp-proto   OTLP HTTP/Protobuf
- @opentelemetry/instrumentation-{http,express,nestjs-core,pg,
  ioredis,pino}                  curated, no `auto-instrumentations-
                                 node` mass-import (anti-bricolage)

Dev dep: pino-pretty (gated by NODE_ENV).

Code:

- apps/portal-bff/src/observability/tracing.ts — OTel `NodeSDK`
  bootstrap. Documents the load-order constraint inline (must be
  the very first import of `main.ts`). Exports nothing — pure
  side-effect file.
- apps/portal-bff/src/observability/observability.module.ts —
  composes ClsModule (UUID per request stored as `request_id`)
  and LoggerModule (pino-pretty in dev / raw JSON in prod,
  LOG_LEVEL env-driven, `/health` excluded from auto-logging).
- apps/portal-bff/src/health/{health.controller,health.module}.ts
  — `GET /api/health` returning `{status, uptimeSeconds, service,
  version}`. Cheap liveness only — no DB / Redis check; that
  belongs to a future `/readiness` once dependencies have a
  readiness story.
- apps/portal-bff/src/config/check-database-url.ts — fail-fast
  validator called from main.ts before NestFactory boots. Catches
  the same family of bug that bit pgweb in #63: a literal special
  char in POSTGRES_PASSWORD that needs URL-encoding in
  DATABASE_URL. Prisma requires a URL string, so we cannot use
  discrete CLI flags here — early validation + clear error message
  is the v1 mitigation. Six unit tests cover happy path, missing
  URL, wrong scheme, encoded special chars, literal `@` in
  password, malformed URL.

Wiring:

- main.ts now `import`s `./observability/tracing` as its first
  line, calls `assertDatabaseUrl()`, then bootstraps Nest with
  `app.useLogger(app.get(Logger))` from nestjs-pino with
  `bufferLogs: true` so early-bootstrap lines are not lost.
- app.module.ts imports ObservabilityModule first, then the
  PrismaModule, then HealthModule.
- .env.example (BFF and infra/local) document the URL-encoding
  constraint on POSTGRES_PASSWORD with the exact char-by-char
  encoding table.

Trace ↔ log correlation is automatic via
`@opentelemetry/instrumentation-pino`: every Pino record gets
`trace_id` / `span_id` injected from the active OTel context.
No CLS gymnastics needed for that specific concern.

ADR-0012 §Confirmation rewritten to clearly distinguish what
landed in this PR (phase 1) from what is wired as the
corresponding feature ADRs ship (CLS keys for session/user/
audience, LOG_USER_ID_SALT, redact list, custom spans, SPA-side
SDK, full integration tests, prod Collector config).

Verified locally:
- pnpm exec nx run-many -t lint test build → 8 projects green,
  4 test suites for portal-bff, 9 unit tests pass.
- `pnpm nx serve portal-bff` boots, `curl /api/health` returns
  the expected JSON; logs are pretty-printed JSON one-liners on
  stdout in dev.
- `pnpm audit --audit-level=moderate` reports 0 vulnerabilities.

package.json

@@ -96,6 +96,7 @@
     "jsonc-eslint-parser": "^2.1.0",
     "lint-staged": "^17.0.0",
     "nx": "22.7.1",
+    "pino-pretty": "^13.1.3",
     "postcss": "^8.5.12",
     "prettier": "^3.8.1",
     "prisma": "^6.19.3",
@@ -119,11 +120,26 @@
     "@nestjs/common": "^11.0.0",
     "@nestjs/core": "^11.0.0",
     "@nestjs/platform-express": "^11.0.0",
+    "@opentelemetry/api": "^1.9.1",
+    "@opentelemetry/exporter-trace-otlp-proto": "^0.217.0",
+    "@opentelemetry/instrumentation-express": "^0.65.0",
+    "@opentelemetry/instrumentation-http": "^0.217.0",
+    "@opentelemetry/instrumentation-ioredis": "^0.65.0",
+    "@opentelemetry/instrumentation-nestjs-core": "^0.63.0",
+    "@opentelemetry/instrumentation-pg": "^0.69.0",
+    "@opentelemetry/instrumentation-pino": "^0.63.0",
+    "@opentelemetry/resources": "^2.7.1",
+    "@opentelemetry/sdk-node": "^0.217.0",
+    "@opentelemetry/semantic-conventions": "^1.40.0",
     "@prisma/client": "^6.19.3",
     "axios": "^1.6.0",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.15.1",
+    "nestjs-cls": "^6.2.0",
+    "nestjs-pino": "^4.6.1",
     "nestjs-prisma": "^0.27.0",
+    "pino": "^10.3.1",
+    "pino-http": "^11.0.0",
     "reflect-metadata": "^0.2.0",
     "rxjs": "~7.8.0"
   }