feat(habit): expose durable recurring-habit HTTP API

[seonghobae]

Summary

Implements #41 as the next reviewable habit.recurring-core slice after #40.

• adds bounded PostgreSQL pool configuration and an exactly-once NestJS shutdown lifecycle
• wires the production Habit service to PostgresHabitRepository without an in-memory fallback
• exposes versioned tenant-scoped routes for habit creation/listing, occurrence generation, idempotent completion commands, and immutable completion history
• derives ownership exclusively from x-workspace-id and validates workspace/habit identifiers before persistence
• parses untrusted recurrence and completion bodies without accepting tenant ownership from JSON
• maps validation, missing records, idempotency conflicts, persistence failures, and unknown failures to bounded credential-free problem details
• adds runtime tests plus habit-service.integration.test.ts over the production NestJS module and disposable PostgreSQL
• proves tenant isolation, recurrence correctness, exact completion replay, conflicting replay rejection, process-restart durability, invalid ownership handling, and credential-free database failures
• documents runtime settings, routes, migration privileges, shutdown behavior, and deferred workflows

Deferred

Authenticated workspace derivation at an API gateway, pause/archive, streak projections, reminders, calendar integration, controlled erasure, and end-user workflow design remain separate reviewable slices.

Validation gate

Merge only when CI, AppGuardrail, Semgrep, Security Scan, Commercial Readiness, CodeRabbit, and all human/security review requirements pass on the exact head with no unresolved actionable findings.

Closes #41

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📥 Commits

Reviewing files that changed from the base of the PR and between cab995e and 2f083cb.

📒 Files selected for processing (10)

• apps/habit-service/migrations/README.md
• apps/habit-service/package.json
• apps/habit-service/src/habit-runtime.test.ts
• apps/habit-service/src/habit-runtime.ts
• apps/habit-service/src/habit-service.integration.test.ts
• apps/habit-service/src/http-boundary.test.ts
• apps/habit-service/src/http-boundary.ts
• apps/habit-service/src/main.ts
• docs/superpowers/plans/2026-08-04-habit-http-api-slice.md
• package.json

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