feat: core tests, bug fixes, API docs rewrite, HTTP compat routes

- Fix state_machine reset_state_progress: reset sequence index before
  validation to prevent out-of-bounds error on state transitions
- Fix video transformer test: use ±1 tolerance for OpenCV interpolation
- Add core integration tests (service_manager, dependencies, messages)
- Add HTTP compat routes (/index.html, POST /api/wifi/scan, hotspot aliases)
- Rewrite clients/docs/API.md to match actual implementation
- Fix BLE unused imports warning
- CEO task planning for next round (ConfigReload, playlist snapshot)

cargo check: 0 warnings, cargo test: 22/22 passed

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

src/plugins/video/state_machine.rs

@@ -149,8 +149,8 @@ impl StateMachine {
     }
 
     fn reset_state_progress(&mut self) -> Result<()> {
-        self.ensure_current_state_valid()?;
         self.current_sequence_index = 0;
+        self.ensure_current_state_valid()?;
         self.current_loop_remaining = self.resolve_current_loop_count()?;
         Ok(())
     }