Replace C Tor with Rust Arti for Tor integration

- Replace C Tor (0.4.8.21) with Rust Arti (1.9.0/arti-client 0.38)
- 70% smaller binary: 21MB xcframework vs 67MB (6.9MB vs 14MB per slice)
- Memory-safe Rust implementation with modern async (tokio)
- Same SOCKS5 proxy interface at 127.0.0.1:39050 for drop-in compatibility
- FFI wrapper (arti-bitchat crate) with C-compatible exports
- Swift TorManager maintains identical public API
- Aggressive size optimization: opt-level=z, lto=fat, panic=abort, strip
- Supports iOS device, iOS simulator (Apple Silicon), and macOS

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

localPackages/Arti/Sources/C/include/arti.h

@@ -0,0 +1,71 @@
+#ifndef ARTI_H
+#define ARTI_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Start Arti with a SOCKS5 proxy.
+ *
+ * @param data_dir Path to data directory for Tor state (C string)
+ * @param socks_port Port for SOCKS5 proxy (e.g., 39050)
+ * @return 0 on success, negative on error:
+ *         -1: already running
+ *         -2: invalid data_dir
+ *         -3: runtime initialization failed
+ *         -4: bootstrap failed
+ */
+int32_t arti_start(const char *data_dir, uint16_t socks_port);
+
+/**
+ * Stop Arti gracefully.
+ *
+ * @return 0 on success, -1 if not running
+ */
+int32_t arti_stop(void);
+
+/**
+ * Check if Arti is currently running.
+ *
+ * @return 1 if running, 0 if not running
+ */
+int32_t arti_is_running(void);
+
+/**
+ * Get the current bootstrap progress (0-100).
+ *
+ * @return Progress percentage
+ */
+int32_t arti_bootstrap_progress(void);
+
+/**
+ * Get the current bootstrap summary string.
+ *
+ * @param buf Buffer to write the summary into
+ * @param len Length of the buffer
+ * @return Number of bytes written, -1 on error
+ */
+int32_t arti_bootstrap_summary(char *buf, int32_t len);
+
+/**
+ * Signal Arti to go dormant (reduce resource usage).
+ *
+ * @return 0 on success, -1 if not running
+ */
+int32_t arti_go_dormant(void);
+
+/**
+ * Signal Arti to wake from dormant mode.
+ *
+ * @return 0 on success, -1 if not running
+ */
+int32_t arti_wake(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ARTI_H */

localPackages/Arti/Sources/C/include/module.modulemap

@@ -0,0 +1,4 @@
+module ArtiC {
+    header "arti.h"
+    export *
+}