DM pairing + Telegram channel improvements (#17)

* feat: Implement DM pairing for channels

- Introduced a new pairing system to manage direct messages from unknown senders.
- Added `PairingStore` to handle pending requests and allowlist management.
- Implemented CLI commands for listing and approving pairing requests.
- Updated Telegram channel to utilize the new pairing logic, including workspace paths for storing pairing data.
- Enhanced WASM channel integration to support pairing functionality.

This feature enhances security by requiring approval for unknown senders before they can interact with the agent.

* Enhance Telegram channel support with media captioning and DM pairing features

- Added support for media captions in Telegram messages, allowing for richer content handling.
- Updated message processing to utilize either text or caption, improving message flexibility.
- Enhanced DM pairing functionality to include approval and listing capabilities for direct messages.
- Updated feature parity documentation to reflect new capabilities and improvements in Telegram integration.

* Update README and BUILDING_CHANNELS documentation for Telegram channel integration

- Enhanced README with instructions for building and running the Telegram channel, including a note on running `./scripts/build-all.sh` for full releases.
- Added detailed steps in BUILDING_CHANNELS.md for building and deploying the Telegram channel, emphasizing the need to run `./channels-src/telegram/build.sh` before building the main crate to ensure updated WASM is included.
- Updated CLI module to expose a new command for pairing with store functionality.

* Implement build script for Telegram channel WASM and enhance pairing error handling

- Added a new `build.rs` script to automate the compilation of the Telegram channel's WASM binary from source, ensuring reproducible builds and emphasizing supply chain security by preventing committed binaries.
- Updated `BUILDING_CHANNELS.md` to reflect the new build process and the importance of not committing compiled binaries.
- Enhanced error handling in the pairing approval process to include rate limiting for failed attempts, improving security and user feedback.

* Remove Telegram channel WASM binary file as part of the build process cleanup, ensuring no committed binaries are present in the repository.

Cargo.lock

@@ -1621,6 +1621,16 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "fs4"
+version = "0.6.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2eeb4ed9e12f43b7fa0baae3f9cdda28352770132ef2e09a23760c29cae8bd47"
+dependencies = [
+ "rustix 0.38.44",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "funty"
 version = "2.0.0"
@@ -2299,6 +2309,7 @@ dependencies = [
  "deadpool-postgres",
  "dirs 6.0.0",
  "dotenvy",
+ "fs4",
  "futures",
  "hkdf",
  "http-body-util",