feat(docs): migrate and reorganize frontend guides for BP panel and file uploads

- Deleted outdated documentation files for BP panel list sorting and Filestore frontend guide.
- Created new documentation files for BP panel list sorting and Filestore frontend guide in the client directory.
- Updated the structure and content to enhance clarity and accessibility for frontend integration with file upload and profile image APIs.
- Ensured consistency in documentation style and improved examples for better developer experience.

src/components/FormElements/PhoneNumberInput/PhoneNumberInput.tsx

@@ -6,6 +6,7 @@ import {
   normalizeToE164,
   PHONE_UI_MAX_LENGTH,
   splitE164ForEditing,
+  toBestEffortE164,
 } from "@/lib/phone/e164";
 import {
   DEFAULT_PHONE_COUNTRY,
@@ -80,8 +81,10 @@ export function PhoneNumberInput({
 
   const emitE164 = useCallback(
     (nationalInput: string, countryCode: CountryCode) => {
-      const e164 = normalizeToE164(nationalInput, countryCode);
-      const next = e164 ?? "";
+      // Preserve the user's input as best-effort E.164 instead of clearing it
+      // to "" whenever it is not yet strictly valid — otherwise a typed number
+      // can silently vanish from the submitted payload.
+      const next = toBestEffortE164(nationalInput, countryCode);
       lastEmitted.current = next;
       onChange(next);
     },
@@ -110,9 +113,12 @@ export function PhoneNumberInput({
       setNational(display.national);
       lastEmitted.current = e164;
       onChange(e164);
-    } else if (!required) {
-      lastEmitted.current = "";
-      onChange("");
+    } else {
+      // Keep what the user typed (as best-effort E.164) so an invalid number is
+      // surfaced by validation rather than silently discarded on blur.
+      const next = toBestEffortE164(national, country);
+      lastEmitted.current = next;
+      onChange(next);
     }
     onBlur?.();
   };