ui: redesign brand icon and fix clipped wordmark

- new mark: measurement-span glyph on rounded brand-gradient badge
  (favicon, inline logo, standalone tmflow-logo.svg)
- wordmark moved from SVG <text> with hardcoded x offsets (clipped
  "Flow" past the 260px viewBox, font-dependent overlap) to plain HTML
  spans — never clips, natural kerning, theme-adaptive
- _app_logo.html params: logo_class, wordmark_class, logo_id (unique
  gradient id when logo appears twice per page)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/frontend/flask_app/templates/components/navbar.html

@@ -51,7 +51,9 @@
             <img src="{{ url_for('static', filename='img/' ~ company_logo) }}" alt="Logo" class="h-10 w-auto"
                  onerror="this.style.display='none'">
           {% else %}
-            {% set logo_class = 'h-10 w-auto' %}
+            {% set logo_class = 'h-9 w-9' %}
+            {% set wordmark_class = 'text-xl' %}
+            {% set logo_id = 'nav' %}
             {% include 'components/_app_logo.html' %}
           {% endif %}
         </a>