fix(sf-fe): decode cad URL param + hide entry sidebar when drawer open

Two prod issues:

1. Analysis page B5 endpoint returned HTTP 400 'Неверный формат
   кадастрового номера' for any cad. Next.js dynamic route delivers
   `params.cad` URL-encoded (':' -> '%3A'). Hooks then ran
   encodeURIComponent on the already-encoded string, producing
   /api/v1/parcels/66%253A41%253A0204016%253A10/analyze; FastAPI
   decoded one layer to '66%3A41%3A0204016%3A10', which the regex
   rejected. Fix: decodeURIComponent the param once at the page
   boundary so downstream consumers (hooks + breadcrumb + Section1)
   work with the canonical '66:41:0204016:10' and encode exactly
   once when building URLs. Also resolves the breadcrumb double-
   encode noted in PR #346 QA.

2. Entry page right-sidebar (CadInput + RecentParcels + ParcelLegend)
   visually overlapped the ParcelDrawer slide-in: both were anchored
   to the right edge with the drawer rendered above as an overlay
   without an opaque backdrop on the sidebar area. Conditional render:
   sidebar only mounts when no parcel is selected, so opening a parcel
   gives the drawer a clean right column.

frontend/src/app/site-finder/analysis/[cad]/page.tsx

@@ -75,8 +75,13 @@ interface PageProps {
 }
 
 export default function AnalysisPage({ params }: PageProps) {
-  // React 19: use() unwraps Promise params (app router pattern)
-  const { cad } = use(params);
+  // React 19: use() unwraps Promise params (app router pattern).
+  // Next.js delivers `cad` URL-encoded (":" -> "%3A"); decode once here so
+  // downstream hooks/components see the canonical "66:41:0204016:10" and can
+  // re-encode exactly once when building API URLs / hrefs (prevents double-
+  // encode that made backend regex reject the cad with HTTP 400).
+  const { cad: cadRaw } = use(params);
+  const cad = decodeURIComponent(cadRaw);
 
   return (
     <main

frontend/src/app/site-finder/page.tsx

@@ -167,22 +167,24 @@ export default function SiteFinderPage() {
           />
         </div>
 
-        {/* Right sidebar */}
-        <div
-          style={{
-            width: 300,
-            flexShrink: 0,
-            padding: "16px 16px 16px 0",
-            display: "flex",
-            flexDirection: "column",
-            gap: 12,
-            overflowY: "auto",
-          }}
-        >
-          <CadInput onSubmit={handleCadSubmit} loading={false} />
-          <RecentParcels />
-          <ParcelLegend />
-        </div>
+        {/* Right sidebar — hidden when ParcelDrawer is open to avoid overlap */}
+        {selectedParcel == null && (
+          <div
+            style={{
+              width: 300,
+              flexShrink: 0,
+              padding: "16px 16px 16px 0",
+              display: "flex",
+              flexDirection: "column",
+              gap: 12,
+              overflowY: "auto",
+            }}
+          >
+            <CadInput onSubmit={handleCadSubmit} loading={false} />
+            <RecentParcels />
+            <ParcelLegend />
+          </div>
+        )}
       </div>
 
       {/* Parcel drawer (slide-in from right) */}