Add FAQ.md with functionality, security, and deployment questions

Covers common questions a junior-to-mid-level engineer would ask:
- Functionality: waiting for services, seeding, migrations, rendering,
  retry tuning, JSON logs, the -- separator, shell behavior
- Security: privileges, secret redaction, path traversal, TLS, scratch
  image rationale, image verification, multi-tenancy
- Deployment: installation methods, image tags, Helm chart scope, data
  sharing via emptyDir, chaining init steps, ARM support, debugging
  CrashLoopBackOff, private registries, building from source
Also links FAQ from README Documentation section and updates CHANGELOG.

Author: mikkeldamsgaard

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- FAQ.md with functionality, security, and deployment questions for junior-to-mid-level engineers
 - Project scaffolding with Go module, CLI framework (cobra), and repo layout
 - `wait-for` subcommand: wait for TCP and HTTP(S) endpoints with retries, exponential backoff, and jitter
 - `internal/retry` package with configurable retry logic, backoff, and jitter