add tool calling, SQLite persistence, group chat, image vision, voice transcription

Major features:
- OpenAI function calling with tool call loop (streaming SSE parsing)
- Built-in tools: spawn_agent (async claude -p), agent_status, kill_agent,
  update_scratch, send_file
- Script-based tool discovery: tools/ dir with --schema convention
- Feishu todo management script (tools/manage_todo)
- SQLite persistence: conversations, messages, config, scratch_area tables
- Sliding window context (100 msgs, slide 50, auto-summarize)
- Conversation summary generation via LLM on window slide
- Group chat support with independent session contexts
- Image understanding: multimodal vision input (base64 to API)
- Voice transcription via faster-whisper Docker service
- Configurable persona stored in DB
- diag command for session diagnostics
- System prompt restructured: persona + tool instructions separated
- RUST_BACKTRACE=1 in service, clippy in deploy pipeline
- .gitignore for config/state/db files

Cargo.toml

@@ -5,13 +5,16 @@ edition = "2021"
 
 [dependencies]
 anyhow = "1"
+base64 = "0.22"
 chrono = { version = "0.4", features = ["serde"] }
 dptree = "0.3"
+libc = "0.2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 serde_yaml = "0.9"
 pulldown-cmark = "0.12"
-reqwest = { version = "0.12", features = ["json"] }
+reqwest = { version = "0.12", features = ["json", "multipart"] }
+rusqlite = { version = "0.32", features = ["bundled"] }
 teloxide = { version = "0.12", features = ["macros"] }
 tokio = { version = "1", features = ["full"] }
 uuid = { version = "1", features = ["v5"] }