Add golden-path examples, Vault guidance, and module documentation

[skyglass]

EXA-ANS-010: Add golden-path examples, Vault guidance, and module documentation

Labels: docs, examples, golden-path, mvp

Use case ID: UC-GOLDEN-PATH

Primary actor: Exasol DBA

Goal: document the simplest production-relevant workflow: check Exasol version
from Ansible and optionally insert the result into a metadata table.

Trigger: DBA installs the MVP collection from a local build or Galaxy.

Preconditions:

• exasol_query and exasol_info exist.
• Standard login_* parameters are implemented.

Scope:

• Update README.md and doc/user_guide.rst.
• Add examples/ playbooks for:
  • version check with exasol_query
  • version facts with exasol_info
  • credentials from Ansible Vault or encrypted inventory variables
  • simple schema/user/grant lifecycle once those modules exist
• Document that modules run on the controller and normally use
  delegate_to: localhost.
• Document runtime dependency installation for pyexasol.

Acceptance criteria:

• README includes a working minimal playbook using the selected collection FQCN.
• User guide documents Ansible Vault credential pattern.
• User guide documents that TLS is enabled by default.
• Examples do not contain real customer credentials or hostnames.
• Documentation states that AD sync and C4/conf D lifecycle automation are out
  of scope for v1.

Implementation notes:

• Keep documentation concise. DBA's stated need is "standard SQL selects, simple
  is good."