feat(marketing): base.html layout + glassmorphism header + button macro

- templates/macros/button.html: 3 variants (primary gradient/glow, secondary,
  ghost) x 3 sizes for reuse across marketing/billing/legal/auth templates
- templates/marketing/base.html: Tailwind v4-scoped layout with FlexiHub
  glassmorphism header (62px, navy/.97, backdrop-blur-xl, .045 border),
  sticky positioning, OG/Twitter meta, Inter font preload, marketing.css
  link, Alpine.js defer, 5-item main nav + Connexion/Demarrer CTAs
- templates/marketing/_footer.html: minimal Phase 2 placeholder with
  legal links + Inverness QC address + info@dictia.ca (full footer in A-2.7)
- templates/marketing/landing.html: minimal hero placeholder (replaced
  in A-2.2 with full hero + cosmic orbs)
- src/marketing/routes.py: landing() now render_template instead of inline HTML
- 7 tests verify template structure, FlexiHub markers, nav, CTAs, legal
  links, no login redirect for anonymous users
- Tailwind CSS rebuilt with new template content scope (cssnano-minified)

templates/macros/button.html

@@ -0,0 +1,20 @@
+{# Reusable button macro — primary (gradient + glow), secondary (white outline), ghost (transparent on dark) #}
+{%- macro button(text, href='#', variant='primary', size='md', icon=None, target=None, rel=None) -%}
+{%- set classes = {
+  'primary': 'grad-bg shadow-cta hover:shadow-cta-hover hover:-translate-y-px',
+  'secondary': 'bg-white text-brand-navy border border-brand-border hover:bg-brand-bg',
+  'ghost': 'text-white border border-white/[0.08] hover:bg-white/[0.05]'
+}[variant] -%}
+{%- set sizing = {
+  'sm': 'px-3 py-1.5 text-sm',
+  'md': 'px-5 py-2.5 text-[15px]',
+  'lg': 'px-6 py-3 text-base'
+}[size] -%}
+<a href="{{ href }}"
+   class="inline-flex items-center justify-center gap-2 rounded-[0.75rem] font-semibold transition-all duration-200 {{ classes }} {{ sizing }}"
+   {% if target %}target="{{ target }}"{% endif %}
+   {% if rel %}rel="{{ rel }}"{% endif %}>
+  <span>{{ text }}</span>
+  {%- if icon -%}<span class="ml-0.5" aria-hidden="true">{{ icon | safe }}</span>{%- endif -%}
+</a>
+{%- endmacro -%}