chore: tighten gitignore, align README stack, formalize D-010 (Ansible)

- .gitignore: add Keycloak/Mythic/Fernet secret patterns (pfx, p12, token, kdbx,
  credentials.json, secrets.json, service-account*.json), MSVC artifacts
  (lib, exp, idb, ilk, tlog), dedup dist/build/ between Python and Node blocks.
- README.md: align Storage line on H38 (testcontainers Postgres for Postgres-
  specific behavior, incl. unit tests of audit log / RBAC / write-only role).
- README.md: align Deploy line on D-007/D-010 — Docker + Ansible playbook,
  reverse proxy explicitly out-of-Mimic.
- README.md: add proprietary internal use notice.
- CHANGELOG.md: convert markdown link to inline URL (no dangling reference).
- tasks/spec-decisions.md: add D-010 (Ansible for deployment playbook).

Addresses code-reviewer M1/M2/M3 + N2/N3/N4/N6 on commit 047583e.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-All notable changes to Mimic. Format inspired by [Keep a Changelog](https://keepachangelog.com).
+All notable changes to Mimic. Format inspired by Keep a Changelog (https://keepachangelog.com).
 Versioning starts at `0.1.0` when sprint 0 lands.
 
 ## [Unreleased]