UI redesign step 1/N: Tailwind foundation + Stitch theme + Login + Wizard

Foundation
- Pull in Tailwind via CDN with the full Stitch design tokens
  (palette, typography, spacing, radius) inline in <head>. Preflight
  disabled so the rest of the legacy inline CSS keeps applying until
  each screen is migrated.
- Add Hanken Grotesk + JetBrains Mono + Material Symbols Outlined
  via Google Fonts.
- Replace the page header with the Stitch dark-slate top bar: brand
  on the left, segmented tab nav in the middle, user pill + logout
  on the right. Floating userBadge removed; renderUserBadge() now
  writes the display name into #headerUserName and wires the
  existing logout button.

Login
- Single card mirroring the Stitch login mockup with icon-prefixed
  inputs (person/lock), focus ring, error banner and a primary CTA
  that includes the login glyph. Setup mode swaps the heading,
  shows the orange info bar with admin_panel_settings glyph and
  changes the button to "Administrator anlegen".

Wizard (Schaltung erfassen)
- Step 1: anbieter button grid in Stitch style — bordered cards
  with a material icon, hover lift and primary-coloured outline.
- Step 2: white card with a "← Anbieter ändern" pill in the
  header, two-column layout (Aktivierungsdaten / Vertragsdaten),
  label-caps form labels, JetBrains-Mono numeric inputs for
  dates/ID/phone and a dashed file-drop zone. Save button gains
  the save glyph.

Other screens (Übersicht, Provisionen, Gelöschte, Administration,
Benutzer) still render in the legacy style — those migrations
follow in the next steps.

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

.gitignore

@@ -19,6 +19,10 @@ uploads/
 .env.*.local
 sessions.db
 
+# Stitch design exports / drafts
+stitch_*.zip
+stitch_*/
+
 # OS / Editor
 .DS_Store
 Thumbs.db