feat(base): scaffold role + meta/README (firewall concern incoming)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

roles/base/README.md

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+# base
+
+Hardened baseline applied to every boma host. Built incrementally; the first concern
+implemented is the **host firewall** (`firewall` tag).
+
+## Firewall (nftables)
+
+Default-deny inbound + east-west allowlisting + permissive egress, per ADR-020. Rules
+are rendered from the shared `firewall_catalog` / `firewall_zones` (in `group_vars/all`)
+by the `resolve_firewall_rules` filter, written to `/etc/nftables.conf`, syntax-checked
+with `nft -c` at render time, and applied with an **auto-rollback safety net**
+(`systemd-run` arms a revert that a follow-up task cancels once connectivity is
+confirmed). The apply sequence lives in tasks rather than a handler so the confirm/cancel
+step is controllable.
+
+`/etc/nftables.d/*.nft` is `include`d by the ruleset — the extension hook the
+`docker_host` role uses for container forward/NAT rules.
+
+### Variables
+See `defaults/main.yml` (`base__firewall_*`). SSH is accepted only on
+`base__firewall_mgmt_interface` (default `wt0`, the NetBird overlay — ADR-016); set it to
+a reachable interface/source until NetBird is built. Set `base__firewall_apply: false` to
+render + validate without applying (used by Molecule).
+
+### Testing
+- `tests/test_firewall_rules.py` — pytest units for the resolver.
+- `make test ROLE=base` — Molecule renders + `nft -c` syntax-checks (never applies; it
+  shares the host kernel). Enforcement + the apply/rollback path are verified at ADR-008
+  Level 2 on staging VMs.

roles/base/defaults/main.yml

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+---

roles/base/handlers/main.yml

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+---

roles/base/meta/main.yml

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+---
+galaxy_info:
+  author: sjat
+  description: Hardened baseline configuration for all boma hosts (Debian 13).
+  license: MIT
+  min_ansible_version: "2.17"
+  platforms:
+    - name: Debian
+      versions:
+        - trixie
+dependencies: []

roles/base/molecule/default/converge.yml

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+---
+- name: Converge
+  hosts: all
+  gather_facts: true
+
+  roles:
+    - role: base

roles/base/molecule/default/molecule.yml

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+---
+dependency:
+  name: galaxy
+  options:
+    requirements-file: ../../requirements.yml
+
+driver:
+  name: docker
+
+platforms:
+  - name: instance
+    # Project-owned image built from .docker/molecule-debian13/Dockerfile
+    # and hosted in the Forgejo container registry.
+    # Build/push with: make molecule-image / make molecule-image-push
+    image: forgejo.nyumbani.baobab.band/sjat/molecule-debian13:latest
+    pre_build_image: true
+    privileged: true          # required for systemd
+    cgroupns_mode: host
+    volumes:
+      - /sys/fs/cgroup:/sys/fs/cgroup:rw
+    command: /lib/systemd/systemd
+
+provisioner:
+  name: ansible
+  inventory:
+    host_vars:
+      instance:
+        ansible_user: root
+
+verifier:
+  name: ansible

roles/base/molecule/default/verify.yml

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+---
+- name: Verify
+  hosts: all
+  gather_facts: true
+
+  tasks:
+    - name: Add verification tasks here
+      ansible.builtin.assert:
+        that: true
+        msg: "Replace this with real assertions"
+      tags: [verify]

roles/base/tasks/main.yml

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+---