feat(ui): breadcrumb navigation across nested pages

Adds a breadcrumb trail to nested views for orientation. Mechanism: a
{% block breadcrumb %} slot in base.html (+ styling) and a shared crumbs()
macro in templates/_macros.html; each nested page fills the block with its
trail (root→current, last item is the current page). Pages without the block
render no bar, so top-level nav roots stay clean.

Applied to: Ansible (browse, schedules, playbook editor, run detail) +
inventory (targets/groups + detail), host_agent (fleet, host detail,
settings), hosts form, settings tabs (ansible/auth/notifications/plugins/
reports + plugin detail), dashboard (list, edit), and alerts (rule form,
maintenance + new). Dynamic labels (host/target/run/dashboard names) come
from the page context — no route changes. All 60 templates Jinja-compile.

Task #873.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

steward/templates/ansible/browse.html

@@ -1,5 +1,13 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Browse Playbooks — Steward{% endblock %}
+{% block breadcrumb %}
+{%- if view_contents is defined -%}
+{{ crumbs([("Ansible", "/ansible/"), ("Browse", "/ansible/browse"), (view_path, "")]) }}
+{%- else -%}
+{{ crumbs([("Ansible", "/ansible/"), ("Browse", "")]) }}
+{%- endif -%}
+{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;">
     <h1 class="page-title" style="margin-bottom:0;">Browse Playbooks</h1>

steward/templates/ansible/inventory/group_detail.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Group: {{ group.name }} — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Inventory", "/ansible/inventory/targets"), ("Groups", "/ansible/inventory/groups"), (group.name, "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;">
     <h1 class="page-title" style="margin-bottom:0;">Group: {{ group.name }}</h1>

steward/templates/ansible/inventory/groups.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Inventory Groups — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Inventory", "/ansible/inventory/targets"), ("Groups", "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;">
     <h1 class="page-title" style="margin-bottom:0;">Inventory Groups</h1>

steward/templates/ansible/inventory/target_detail.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Target: {{ target.name }} — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Inventory", "/ansible/inventory/targets"), ("Targets", "/ansible/inventory/targets"), (target.name, "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;">
     <h1 class="page-title" style="margin-bottom:0;">Target: {{ target.name }}</h1>

steward/templates/ansible/inventory/targets.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Inventory Targets — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Inventory", "/ansible/inventory/targets"), ("Targets", "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;">
     <h1 class="page-title" style="margin-bottom:0;">Inventory Targets</h1>

steward/templates/ansible/playbook_editor.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}{{ "Edit" if editing else "New" }} Playbook — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Browse", "/ansible/browse"), (("Edit " ~ playbook_path) if editing else "New playbook", "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.25rem;gap:1rem;flex-wrap:wrap;">
   <h1 class="page-title" style="margin-bottom:0;">{{ "Edit playbook" if editing else "New playbook" }}</h1>

steward/templates/ansible/run_detail.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Run {{ run.id[:8] }} — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Run " ~ run.id[:8], "")]) }}{% endblock %}
 {% block content %}
 <div style="display:flex;align-items:center;gap:1rem;margin-bottom:1.5rem;">
     <a href="/ansible/" class="btn btn-ghost btn-sm">← Runs</a>

steward/templates/ansible/schedules.html

@@ -1,5 +1,7 @@
 {% extends "base.html" %}
+{% from "_macros.html" import crumbs %}
 {% block title %}Ansible Schedules — Steward{% endblock %}
+{% block breadcrumb %}{{ crumbs([("Ansible", "/ansible/"), ("Schedules", "")]) }}{% endblock %}
 
 {% macro fmt_interval(secs) %}
 {%- set m = {300: "every 5 min", 3600: "hourly", 21600: "every 6h", 43200: "every 12h", 86400: "daily", 604800: "weekly"} -%}