fix: restore working injector.js + add missing get:decrypted-config handler

Restored injector.js from v2.0.14 (commit 9a11896) which:
- Requests decrypted config from background via get:decrypted-config
  message instead of passing empty arrays when data is encrypted
- Handles the identity.profiles merge correctly for background responses
- Passes ss_settings directly (not checking _ssLocalEncrypted which
  caused settings loss)

Added missing get:decrypted-config message handler to service-worker.js
which returns decrypted mappings, identity, and settings via Storage
module.

https://claude.ai/code/session_01KF4i7Ra7zCEDskxDBaNtcT

src/options/options.html

@@ -629,7 +629,7 @@
     </section>
 
     <footer>
-      <p>Silent Send v0.9.18</p>
+      <p>Silent Send v0.9.19</p>
       <p style="font-size:11px;color:#9ca3af;margin-top:6px;max-width:600px">
         Silent Send is a convenience tool, not a security guarantee. Third-party sites may change how they send data at any time, which can cause missed substitutions without warning. You are responsible for verifying your data before sending. See the <a href="https://github.com/outis1one/silent-send/blob/main/LICENSE" target="_blank" style="color:#6b7280">LICENSE</a> for full terms.
       </p>