docs: improve auth flow documentation and fix email confirmation redirect

**Auth Callback Improvements:**
- Fix default redirect from /clients to /epd/clients (correct route)
- Add smart detection for password vs magic link users
- Password signup users now go directly to /epd/clients after email confirmation
- Magic link users still get optional /set-password page

**Documentation:**
- Add comprehensive AUTH_FLOW_EXPLAINED.md with step-by-step flow diagrams
- Update RELEASE_AUTH_IMPROVEMENTS.md with magic link migration instructions
- Update emails/README.md with aispeedrun.nl redirect URL configuration
- Document Site URL vs Redirect URLs difference
- Add troubleshooting for common issues (localhost in emails, invalid redirect)

**Key Changes:**
- Email confirmation now correctly redirects password users to EPD
- Clear instructions for Supabase configuration (Site URL + Redirect URLs)
- Both development and production URLs documented for dual environment support

All documentation includes practical examples and FAQ section.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/emails/README.md

@@ -28,12 +28,38 @@ Deze directory bevat HTML email templates die gebruikt kunnen worden in Supabase
 
 ## Hoe te gebruiken in Supabase
 
+### Stap 1: Site URL Configureren
+
+**BELANGRIJK:** Zorg eerst dat je Site URL correct is ingesteld, anders verwijzen alle email links naar localhost!
+
 1. Log in op je Supabase Dashboard
-2. Ga naar **Authentication** → **Email Templates**
-3. Selecteer het juiste template type (Confirm signup of Reset Password)
-4. Kopieer de volledige HTML inhoud van het corresponderende `.html` bestand
-5. Plak deze in het Supabase email template veld
-6. Klik op **Save**
+2. Ga naar **Authentication** → **URL Configuration**
+3. Stel de **Site URL** in:
+   - **Development:** `http://localhost:3000`
+   - **Production:** `https://aispeedrun.nl`
+4. Voeg de volgende **Redirect URLs** toe (één per regel):
+   ```
+   http://localhost:3000/auth/callback
+   http://localhost:3000/update-password
+   http://localhost:3000/set-password
+   http://localhost:3000/reset-password
+   https://aispeedrun.nl/auth/callback
+   https://aispeedrun.nl/update-password
+   https://aispeedrun.nl/set-password
+   https://aispeedrun.nl/reset-password
+   ```
+
+   **Note:** Je kunt zowel localhost als productie URLs toevoegen, zodat beide omgevingen werken.
+
+5. Klik op **Save**
+
+### Stap 2: Email Templates Instellen
+
+1. Ga naar **Authentication** → **Email Templates**
+2. Selecteer het juiste template type (Confirm signup of Reset Password)
+3. Kopieer de volledige HTML inhoud van het corresponderende `.html` bestand
+4. Plak deze in het Supabase email template veld
+5. Klik op **Save**
 
 ## Design Kenmerken