mAi: #112 - fix Fristenrechner Akte-picker icon overlap

The Akte-picker (Step 1) wraps its magnifying-glass icon + input in a
flexbox row (`.fristen-step1-search-row`) with `gap: 0.5rem`, expecting
the icon to participate in the flex layout. But the shared
`.fristen-search-icon` rule (used by the B2 search input) sets
`position: absolute; left: 0.875rem;` — and the step1-scoped override
only tweaked color + flex-shrink without resetting `position`.

Result: the icon was absolutely-positioned out of the flex flow and
overlapped the input text (since `.fristen-akte-search` has no
padding-left). Resetting `position: static` for the step1 context lets
flexbox + gap handle the spacing naturally — same pattern as
`.fristen-row-search-panel-input-wrap`, which already works.

Audited other search inputs with leading magnifying-glass icons:

- `.glossar-search` (Glossary, Courts, Links, Team, AdminTeam,
  AdminEventTypes) — wrap `.glossar-search-wrap` is `position: relative`,
  input has `padding: 0.65rem 4.5rem 0.65rem 2.5rem`. Fine.
- `.projects-search-input` (/projects index) — wrap is
  `position: relative`, input has `padding: 0.5rem 0.75rem 0.5rem 2.4rem`.
  Fine.
- `.fristen-search-input` (Fristenrechner B2) — wrap `.fristen-search-row`
  is `position: relative`, input has
  `padding: 0.75rem 2.5rem 0.75rem 2.6rem`. Fine.
- `.fristen-row-search-panel-input` (Fristenrechner row-search panel) —
  pure flex layout with `gap`, icon non-positioned. Fine.
- `.sidebar-search-input` (global sidebar search) — pure flex layout.
  Fine.
- Other search inputs (`event-search-input`, `event-type-search`,
  `submissions-new-search`, submissions index) have no leading icon.
  N/A.

frontend/src/styles/global.css

@@ -8429,6 +8429,7 @@ input.rule-mode-custom {
 }
 
 .fristen-step1-search-row .fristen-search-icon {
+    position: static;
     color: var(--color-muted, #666);
     flex-shrink: 0;
 }