refactor: split main.rs into 7 modules, add life loop with timer system

Structure:
  main.rs (534)   — entry, handler, prompt building
  config.rs (52)  — config structs
  state.rs (358)  — AppState, SQLite, persistence
  tools.rs (665)  — tool definitions, execution, subagent management
  stream.rs (776) — OpenAI/Claude streaming, system prompt
  display.rs (220)— markdown rendering, message formatting
  life.rs (87)    — life loop heartbeat, timer firing

New features:
- Life Loop: background tokio task, 30s heartbeat, scans timers table
- Timer tools: set_timer (relative/absolute/cron), list_timers, cancel_timer
- inner_state table for life loop's own context
- cron crate for recurring schedule parsing

Zero logic changes in the refactor — pure structural split.

src/config.rs

@@ -0,0 +1,52 @@
+use serde::Deserialize;
+
+#[derive(Deserialize)]
+pub struct Config {
+    #[serde(default = "default_name")]
+    pub name: String,
+    pub tg: TgConfig,
+    pub auth: AuthConfig,
+    pub session: SessionConfig,
+    #[serde(default)]
+    pub backend: BackendConfig,
+    #[serde(default)]
+    pub whisper_url: Option<String>,
+}
+
+fn default_name() -> String {
+    "noc".to_string()
+}
+
+#[derive(Deserialize, Clone, Default)]
+#[serde(tag = "type")]
+pub enum BackendConfig {
+    #[serde(rename = "claude")]
+    #[default]
+    Claude,
+    #[serde(rename = "openai")]
+    OpenAI {
+        endpoint: String,
+        model: String,
+        #[serde(default = "default_api_key")]
+        api_key: String,
+    },
+}
+
+fn default_api_key() -> String {
+    "unused".to_string()
+}
+
+#[derive(Deserialize)]
+pub struct TgConfig {
+    pub key: String,
+}
+
+#[derive(Deserialize)]
+pub struct AuthConfig {
+    pub passphrase: String,
+}
+
+#[derive(Deserialize)]
+pub struct SessionConfig {
+    pub refresh_hour: u32,
+}