Phase 1 AI visibility: job-led IA migration kickoff

## Goal

Begin the job-led IA migration under `/influxdb3/enterprise/`. Six task-oriented sections plus deploy; engine documentation lives once; deployment pages stay thin (only what genuinely differs across managed / self-managed / Kubernetes).

Parent: #7230

## Tasks

### IA skeleton

- [ ] Stand up section landing pages under `/influxdb3/enterprise/`:
- `/get-started/`
- `/concepts/`
- `/collect/`
- `/query/`
- `/process/`
- `/operate/`
- `/integrate/`
- `/deploy/` (with `/managed/`, `/self-managed/`, `/kubernetes/` subsections)
- [ ] Move existing content into new sections (case-by-case audit per page)
- [ ] Add 301 redirects for moved URLs
- [ ] Confirm `/reference/` placement as a top-level sibling (not nested under Enterprise)

### IA decisions to resolve before migration locks

- [ ] Where does `/concepts/` live? Inside `/enterprise/` (current lean) or as a top-level sibling like `/reference/`?
- [ ] Where does the Processing Engine sit? Under `/process/` (job-led) or `/concepts/`?

### Decision pages (citation-worthy)

- [ ] "Choosing a write path" decision page — Telegraf vs. line protocol vs. Kafka vs. client library matrix
- [ ] Optional: per-competitor comparison pages ("InfluxDB 3 vs ClickHouse", "vs TimescaleDB", "vs Postgres", "vs Prometheus") — coordinate with marketing's competitive overhaul rather than own outright

### FAQ surface

- [ ] FAQ blocks on top product, comparison, and reference index pages, wrapped in `FAQPage` JSON-LD
- [ ] Coordinate with #7202 (`/platform/faq.md` FAQ + JSON-LD)

## Out of scope

- Phase 0 cleanup (separate issue)
- Phase 2 sharing-mechanism design (separate design-review issue) — the IA decides *what goes where*; Phase 2 decides *how shared content is delivered*
- Marketing-led comparison pages

Start by reviewing the existing content under /influxdb3/enterprise/ and the parent issue #7230, then resolve where /concepts/ and the Processing Engine belong. Done means the section structure is established, content is audited and moved, 301 redirects are added, /reference/ placement is confirmed, and the specified decision and FAQ surfaces are addressed.

Written by the indexing model from the issue text.