Reorganize repository into monorepo structure

Restructured the project to support multiple frontend applications:
- Move web app to web/ directory
- Create pezkuwi-sdk-ui/ for Polkadot SDK clone (planned)
- Create mobile/ directory for mobile app development
- Add shared/ directory with common utilities, types, and blockchain code
- Update README.md with comprehensive documentation
- Remove obsolete DKSweb/ directory

This monorepo structure enables better code sharing and organized
development across web, mobile, and SDK UI projects.

web/supabase/migrations/003_fix_profile_creation.sql

@@ -0,0 +1,48 @@
+-- ========================================
+-- Fix Profile Creation Issue
+-- ========================================
+-- Adds INSERT policy and makes username nullable
+
+-- Make username nullable and add default (must be done before policies)
+ALTER TABLE public.profiles
+  ALTER COLUMN username DROP NOT NULL;
+
+ALTER TABLE public.profiles
+  ALTER COLUMN username SET DEFAULT '';
+
+-- Drop ALL existing policies to start fresh
+DROP POLICY IF EXISTS "Users can view their own profile" ON public.profiles;
+DROP POLICY IF EXISTS "Users can update their own profile" ON public.profiles;
+DROP POLICY IF EXISTS "Public profiles are viewable by everyone" ON public.profiles;
+DROP POLICY IF EXISTS "Users can insert their own profile" ON public.profiles;
+
+-- Recreate policies with proper permissions
+-- SELECT: Users can view their own profile
+CREATE POLICY "Users can view their own profile"
+  ON public.profiles FOR SELECT
+  USING (auth.uid() = id);
+
+-- INSERT: Users can create their own profile only
+CREATE POLICY "Users can insert their own profile"
+  ON public.profiles FOR INSERT
+  WITH CHECK (auth.uid() = id);
+
+-- UPDATE: Users can update their own profile only
+CREATE POLICY "Users can update their own profile"
+  ON public.profiles FOR UPDATE
+  USING (auth.uid() = id)
+  WITH CHECK (auth.uid() = id);
+
+-- PUBLIC SELECT: Allow everyone to view public profile info
+CREATE POLICY "Public profiles are viewable by everyone"
+  ON public.profiles FOR SELECT
+  USING (true);
+
+-- Success message
+DO $$
+BEGIN
+  RAISE NOTICE '========================================';
+  RAISE NOTICE 'Profile creation fix applied successfully!';
+  RAISE NOTICE 'Users can now create and update their profiles.';
+  RAISE NOTICE '========================================';
+END $$;