fix(partage): smtp view missing in schema + thanks redirect broken

- Add v_smtp_active VIEW to schema.sql (was only in migration 012,
  causing SmtpRelay::isConfigured() to always return false on fresh installs)
- Change thanks redirect from /partage/thanks.php to /partage/thanks
  (nginx 'location ~ \.php$ { deny all }' blocked the .php URL)
- Route /partage/thanks in index.php before slug validation
- Guard App::boot() in thanks.php to avoid double-boot when included

app/storage/schema.sql

@@ -341,6 +341,9 @@ CREATE TABLE IF NOT EXISTS smtp_settings (
 
 INSERT OR IGNORE INTO smtp_settings (id) VALUES (1);
 
+CREATE VIEW IF NOT EXISTS v_smtp_active AS
+SELECT * FROM smtp_settings WHERE id = 1;
+
 -- ============================================================================
 -- APROPOS CONTENTS (structured data for the "À propos" page)
 -- ============================================================================