feat(setup): quick onboarding, preserve .env vars, clean up boot logging (#821)

* feat(setup): quick onboarding, preserve .env vars, clean up boot logging (#751, #674)

- Add upsert_bootstrap_vars() to preserve user-added .env vars on re-onboarding
- Add --quick mode: auto-defaults DB + security, asks only LLM provider (2 steps)
- Auto-triggered onboarding uses quick mode for near-instant first run
- Fix NEAR AI model fetch to use cloud-api.near.ai when API key is set
- Handle missing WASM tools/channels directories gracefully
- Downgrade all boot/shutdown tracing::info! to debug (boot screen shows user output)

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(setup): gate env_backend variable behind postgres feature flag [skip-regression-check]

Clippy lint fix — not a behavioral change, just moving a variable declaration
inside the cfg(feature = "postgres") block where it's used.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(review): address PR review comments

- WASM loaders: use tokio::fs::metadata, only treat NotFound as empty,
  propagate other IO errors, handle TOCTOU in read_dir
- bootstrap: only ignore NotFound in read_to_string, propagate other errors
- wizard: restore print_info/print_success for migrations in interactive
  mode (gated by !config.quick), keep tracing::debug for diagnostics
- tests: use shared crate::config::helpers::ENV_MUTEX instead of separate
  NEARAI_ENV_MUTEX to prevent cross-test env var races
- README: fix quick mode description to mention model selection, clarify
  auto_setup_database may prompt when DATABASE_URL is set

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* feat(setup): skip prompts for DATABASE_URL in quick mode [skip-regression-check]

auto_setup_database() now uses DATABASE_URL directly without calling
step_database_postgres() (which prompts for confirmation). Quick mode
should be fully non-interactive when env vars are already set.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

* fix(cli): update --quick help text to mention model selection [skip-regression-check]

Co-Authored-By: Claude Opus 4.6 <[email protected]>

---------

Co-authored-by: Claude Opus 4.6 <[email protected]>

src/cli/mod.rs

@@ -94,12 +94,16 @@ pub enum Command {
         skip_auth: bool,
 
         /// Reconfigure channels only
-        #[arg(long, conflicts_with = "provider_only")]
+        #[arg(long, conflicts_with_all = ["provider_only", "quick"])]
         channels_only: bool,
 
         /// Reconfigure LLM provider and model only
-        #[arg(long, conflicts_with = "channels_only")]
+        #[arg(long, conflicts_with_all = ["channels_only", "quick"])]
         provider_only: bool,
+
+        /// Quick setup: auto-defaults everything except LLM provider and model
+        #[arg(long, conflicts_with_all = ["channels_only", "provider_only"])]
+        quick: bool,
     },
 
     /// Manage configuration settings