refactor: rename database → storage

More semantically accurate: contains SQLite files, schema, fixtures, test data.
Updated all references in code, scripts, docs.

docs/DEPLOYMENT_STEPS.md

@@ -24,7 +24,7 @@ This deploys all files to `/var/www/posterg/`:
 - `public/` → `/var/www/posterg/public/`
 - `includes/` → `/var/www/posterg/includes/`
 - `config/` → `/var/www/posterg/config/`
-- `database/` → `/var/www/posterg/database/`
+- `storage/` → `/var/www/posterg/storage/`
 - `src/` → `/var/www/posterg/lib/`
 
 ### 3. Update Nginx Configuration
@@ -59,7 +59,7 @@ just server-status
 Check:
 - https://posterg.erg.be/ (should work)
 - https://posterg.erg.be/admin/ (should work)
-- https://posterg.erg.be/database/test.db (should 404 ✅)
+- https://posterg.erg.be/storage/test.db (should 404 ✅)
 
 ---
 
@@ -84,7 +84,7 @@ just deploy-database
 ```
 
 This will:
-1. Upload `database/test.db` to server
+1. Upload `storage/test.db` to server
 2. Set correct permissions
 3. Warn before overwriting
 
@@ -174,7 +174,7 @@ jj edit <previous-change-id>
 - [ ] SSH to server and apply nginx config
 - [ ] `sudo systemctl reload nginx`
 - [ ] Verify site works: https://posterg.erg.be/
-- [ ] Verify security: https://posterg.erg.be/database/test.db → 404
+- [ ] Verify security: https://posterg.erg.be/storage/test.db → 404
 - [ ] Test admin: https://posterg.erg.be/admin/
 - [ ] Deploy database (if needed): `just deploy-database`