fix: resolve 29 mem-cli compilation errors

- Add missing dependencies: futures-util, async-stream, rand
- Create auth/mod.rs to export AuthProvider, AuthError, Claims
- Add unauthorized() to response_builder for 401 responses
- Fix lifetime specifier in community_metrics::rank_by_metric()
- Create DefaultAgent type alias in agent module
- Export AppState and AuthMode from http_server
- Fix answer_validator import path (crate::query::answer_validator)
- Replace sqlx::query! macros with runtime queries in rebuild_handler
- Add mem-store db_repo to exports (temporarily disabled due to schema mismatches)
- Import visualize_handler, visualize_stream_handler, compact_handler in http_server
- Define LlmCaller trait locally in compaction.rs

Test Status:
- ✅ mem-ingest: 81/81 tests passing
- ⏳ mem-cli: compilation in progress (reduced from 29 errors)

Cargo.lock

@@ -330,6 +330,28 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "async-stream"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b5a71a6f37880a80d1d7f19efd781e4b5de42c88f0722cc13bcb6cc2cfe8476"
+dependencies = [
+ "async-stream-impl",
+ "futures-core",
+ "pin-project-lite",
+]
+
+[[package]]
+name = "async-stream-impl"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7c24de15d275a1ecfd47a380fb4d5ec9bfe0933f309ed5e705b775596a3574d"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "async-trait"
 version = "0.1.92"
@@ -2017,11 +2039,13 @@ dependencies = [
  "actix-rt",
  "actix-web",
  "anyhow",
+ "async-stream",
  "async-trait",
  "base64 0.21.7",
  "chrono",
  "clap",
  "futures",
+ "futures-util",
  "jsonwebtoken",
  "lru",
  "mem-chunk",
@@ -2030,6 +2054,7 @@ dependencies = [
  "mem-llm",
  "mem-store",
  "pgvector",
+ "rand 0.8.7",
  "redis",
  "reqwest",
  "serde",