Feature: Add Insecure SSL support for electrum server

[newtonick]

Dependency on bitcoindevkit/bdk-ffi#975 unless I want to fork bdk-ffi in the short term.

Testing Notes:

Switching bdk-swift between local and remote

Hellbender depends on bdk-swift (BitcoinDevKit) via SPM. During normal development it uses the remote release. When testing local bdk-ffi changes (e.g. the v2.3.0-ssl-patch branch), switch to the local copy.

Switch to local bdk-swift

export SOURCE=~"/Source"

1. In $SOURCE/bdk-swift/Package.swift, change the binary target to use a local path:

   .binaryTarget(name: "bdkFFI", path: "./bdkFFI.xcframework"),

2. Build the patched xcframework from bdk-ffi (must be on the correct branch):

   cd $SOURCE/bdk-ffi/bdk-swift && ./build-xcframework-dev.sh

3. Move and rename the output:

   rm -rf $SOURCE/bdk-swift/bdkFFI.xcframework
   mv $SOURCE/bdk-ffi/bdk-swift/bdkffi.xcframework $SOURCE/bdk-swift/bdkFFI.xcframework

4. Regenerate Swift bindings (the build script writes to bdk-ffi's sibling bdk-swift, so copy manually if needed):

   cd $SOURCE/bdk-ffi/bdk-ffi && cargo run --bin uniffi-bindgen generate \
     --library ./target/aarch64-apple-ios/debug/libbdkffi.dylib \
     --language swift --out-dir $SOURCE/bdk-swift/Sources/BitcoinDevKit --no-format

5. In Xcode: remove the remote bdk-swift package dependency, then File → Add Package Dependencies → Add Local... and select $SOURCE/bdk-swift.
6. Clear DerivedData if Xcode uses stale cached headers:

   rm -rf ~/Library/Developer/Xcode/DerivedData/hellbender-*

Switch back to remote bdk-swift

1. In $SOURCE/bdk-swift/Package.swift, restore the remote binary target:

   .binaryTarget(
       name: "bdkFFI",
       url: "https://github.com/bitcoindevkit/bdk-swift/releases/download/2.3.0/bdkFFI.xcframework.zip",
       checksum: "f2224beafaf90415b650e17b4944cba74b553dcc97bb3c5b5359359887bd18f7"),

2. In Xcode: remove the local bdk-swift package dependency.
3. Add remote package: + → https://github.com/bitcoindevkit/bdk-swift → Exact Version 2.3.1 → Add BitcoinDevKit to the hellbender target.

[newtonick]

I expect the build and analyze GitHub action to fail unless BDK is updated or the Packaged is updated to point to a forked version.

[newtonick]

I decided to fork bdk-ffi and bdk-swift. I added one single commit (newtonick/bdk-ffi@94099a7) off of v2.3.1. My intention is to go back to proper BDK v3 once my PR is merged.