security: fix vulnerabilities 1-7 from security audit

- Fix #1: Share handler IDOR - enforce owner check on share operations
- Fix #2: list_files_query IDOR - bind folder queries to authenticated user
- Fix #3: Dedup handler IDOR - restrict dedup operations to file owner
- Fix #4: Trash handler OptionalAuthUser - require full AuthUser
- Fix #5: Error info leakage - sanitize 500 error responses
- Fix #6: Chunked upload IDOR - bind upload sessions to user_id,
  add verify_session_owner() check on all session operations
- Fix #7: CSP unsafe-inline removal - migrate all inline scripts,
  styles and event handlers to external files, tighten CSP to
  script-src 'self'; style-src 'self'

New files:
  - static/js/core/theme-init.js (render-blocking theme init)
  - static/js/core/sw-register.js (service worker registration)
  - static/css/views/device-verify.css (extracted inline styles)
  - static/js/views/device-verify/device-verify.js (extracted inline script)

src/interfaces/api/routes.rs

@@ -288,10 +288,9 @@ pub fn create_api_routes(app_state: &Arc<AppState>) -> Router<Arc<AppState>> {
             "/blob/{hash}",
             get(super::handlers::dedup_handler::DedupHandler::get_blob),
         )
-        .route(
-            "/blob/{hash}",
-            delete(super::handlers::dedup_handler::DedupHandler::remove_reference),
-        )
+        // NOTE: remove_reference is intentionally NOT exposed as a public
+        // endpoint — ref_count management is an internal concern handled
+        // automatically when files are deleted via the file API.
         .route(
             "/recalculate",
             post(super::handlers::dedup_handler::DedupHandler::recalculate_stats),