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.

Cargo.lock

@@ -161,6 +161,18 @@ version = "0.8.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
 
+[[package]]
+name = "cron"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "089df96cf6a25253b4b6b6744d86f91150a3d4df546f31a95def47976b8cba97"
+dependencies = [
+ "chrono",
+ "once_cell",
+ "phf",
+ "winnow",
+]
+
 [[package]]
 name = "darling"
 version = "0.13.4"
@@ -1038,6 +1050,7 @@ dependencies = [
  "anyhow",
  "base64 0.22.1",
  "chrono",
+ "cron",
  "dptree",
  "libc",
  "pulldown-cmark",
@@ -1150,6 +1163,48 @@ version = "2.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 
+[[package]]
+name = "phf"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd6780a80ae0c52cc120a26a1a42c1ae51b247a253e4e06113d23d2c2edd078"
+dependencies = [
+ "phf_macros",
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_generator"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c80231409c20246a13fddb31776fb942c38553c51e871f8cbd687a4cfb5843d"
+dependencies = [
+ "phf_shared",
+ "rand",
+]
+
+[[package]]
+name = "phf_macros"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f84ac04429c13a7ff43785d75ad27569f2951ce0ffd30a3321230db2fc727216"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67eabc2ef2a60eb7faa00097bd1ffdb5bd28e62bf39990626a582201b7a754e5"
+dependencies = [
+ "siphasher",
+]
+
 [[package]]
 name = "pin-project"
 version = "1.1.11"
@@ -1268,6 +1323,21 @@ version = "6.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
 
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+
 [[package]]
 name = "rc-box"
 version = "1.3.0"
@@ -1647,6 +1717,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "siphasher"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2aa850e253778c88a04c3d7323b043aeda9d3e30d5971937c1855769763678e"
+
 [[package]]
 name = "slab"
 version = "0.4.12"
@@ -2552,6 +2628,15 @@ version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
 
+[[package]]
+name = "winnow"
+version = "0.7.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df79d97927682d2fd8adb29682d1140b343be4ac0f08fd68b7765d9c059d3945"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "winreg"
 version = "0.50.0"