fix(ios): rebuild chanora_bridge.framework on every Xcode build, not just pod install

The podspec's prepare_command only fires on `pod install`. Once a
framework was generated, Rust source changes were silently ignored
because Xcode kept re-bundling the stale framework into Runner.app.
Manifested today as: ran `cargo build --release --target
aarch64-apple-ios` to pick up the lenient voice_join fix, ran
`flutter build ios`, but Runner.app/Frameworks/chanora_bridge.
framework/chanora_bridge was still the framework from the previous
pod install (16:10) not the just-built 18:30 dylib.

Add an explicit `script_phase` to the podspec that re-runs:
  1. cargo build --release --target aarch64-apple-ios -p chanora_bridge
  2. cp dylib into Frameworks/chanora_bridge.framework/chanora_bridge
  3. install_name_tool -id @rpath/...

on every Xcode 'Build', not just on pod install. The script short-
circuits when the framework's binary mtime is newer than the cargo
output (fast no-op on incremental builds where Rust didn't change).

Side effect: every Xcode build now invokes cargo, which can take
~5 s on a warm cache and ~1 min cold. This is the right trade-off
because the previous behavior silently shipped stale Rust code.

apps/chanora_flutter/ios/chanora_bridge.podspec

@@ -100,6 +100,52 @@ PLIST
   # Runner.app/Frameworks/ with Embed & Sign automatically.
   s.vendored_frameworks = 'Frameworks/chanora_bridge.framework'
 
+  # Re-run the cargo build + framework wrap on every Xcode build,
+  # not only on `pod install`. The `prepare_command` above runs
+  # once per `pod install` which is too sticky — Rust source
+  # changes were getting silently ignored because Xcode happily
+  # re-bundled the stale framework. This script_phase shells out to
+  # cargo on every Xcode "Build" so the framework is always in sync
+  # with the current Rust workspace.
+  #
+  # `:execution_position => :before_compile` runs the script before
+  # Xcode's CompileSources phase, so by the time the linker / embed
+  # step sees `Frameworks/chanora_bridge.framework`, it is fresh.
+  s.script_phase = {
+    :name => 'Rebuild chanora_bridge.framework from Rust',
+    :script => <<-SCRIPT,
+      set -e
+      REPO_ROOT="$(cd "${PODS_TARGET_SRCROOT}/../../.." && pwd)"
+      BRIDGE="$REPO_ROOT/target/aarch64-apple-ios/release/libchanora_bridge.dylib"
+
+      echo "[chanora_bridge script_phase] cargo build aarch64-apple-ios"
+      cd "$REPO_ROOT"
+      PATH="$HOME/.cargo/bin:$PATH" \\
+        IPHONEOS_DEPLOYMENT_TARGET=13.0 \\
+        CMAKE_POLICY_VERSION_MINIMUM=3.5 \\
+        CMAKE_OSX_DEPLOYMENT_TARGET=13.0 \\
+        cargo build --release --target aarch64-apple-ios -p chanora_bridge
+
+      cd "$REPO_ROOT/apps/chanora_flutter/ios"
+      FW=Frameworks/chanora_bridge.framework
+
+      # Skip the wrap step if the framework's binary is already
+      # up-to-date with the cargo output (fast no-op on incremental
+      # builds where Rust didn't change).
+      if [ -f "$FW/chanora_bridge" ] && [ "$FW/chanora_bridge" -nt "$BRIDGE" ]; then
+        echo "[chanora_bridge script_phase] framework already up-to-date"
+        exit 0
+      fi
+
+      mkdir -p "$FW"
+      cp "$BRIDGE" "$FW/chanora_bridge"
+      install_name_tool -id "@rpath/chanora_bridge.framework/chanora_bridge" \\
+                        "$FW/chanora_bridge"
+      echo "[chanora_bridge script_phase] framework refreshed"
+    SCRIPT
+    :execution_position => :before_compile,
+  }
+
   # The pod has no Objective-C sources; it's purely a framework
   # carrier. Suppress CocoaPods's source-file warning.
   s.source_files = 'Frameworks/chanora_bridge.framework/Headers/*.h'