feat: rebrand Hemmelig to paste.es for cloudhost.es

- Set Spanish as default language with ephemeral/encrypted privacy focus
- Translate all user-facing strings and legal pages to Spanish
- Replace Norwegian flag with Spanish flag in footer
- Remove Hemmelig/terces.cloud links, add cloudhost.es sponsorship
- Rewrite PrivacyPage: zero data collection, ephemeral design emphasis
- Rewrite TermsPage: Spanish law, RGPD, paste.es/CloudHost.es references
- Update PWA manifest, HTML meta tags, package.json branding
- Rename webhook headers to X-Paste-Event / X-Paste-Signature
- Update API docs title and contact to paste.es / cloudhost.es

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/upgrade.md

@@ -0,0 +1,33 @@
+# Upgrading from v6 to v7
+
+## ⚠️ Breaking Changes - Fresh Start Required
+
+**v7 is a complete rewrite and is NOT backwards compatible with v6.** Due to fundamental changes in the encryption and password hashing algorithms, migration of existing data is not possible.
+
+### What Changed
+
+| Component            | v6                  | v7                      |
+| -------------------- | ------------------- | ----------------------- |
+| Encryption Algorithm | Different algorithm | AES-256-GCM with PBKDF2 |
+| Password Hashing     | Different algorithm | Updated secure hashing  |
+| Database Schema      | Previous schema     | New schema structure    |
+
+### Why Migration Is Not Possible
+
+1. **Encryption Algorithm Change:** Secrets encrypted with the v6 algorithm cannot be decrypted with v7's implementation. Since the server never stores decryption keys (zero-knowledge architecture), there is no way to re-encrypt existing secrets.
+
+2. **Password Algorithm Change:** User passwords are hashed differently in v7. Existing password hashes from v6 cannot be verified or converted.
+
+### Upgrade Steps
+
+1. **Backup v6 data** (for reference only - it cannot be migrated)
+2. **Stop your v6 instance**
+3. **Deploy v7 with a fresh database** - See [Docker Guide](docker.md) for deployment instructions
+4. **Re-create user accounts**
+5. **Inform users** that existing secrets are no longer accessible
+
+### Important Notes
+
+- No migration scripts are provided or planned
+- Users must register new accounts in v7
+- Consider running v6 in read-only mode temporarily to allow users to retrieve unexpired secrets before shutdown