refactor(kon): clean up storage and cloud-providers — remove unused deps, add safety docs

- Remove unused chrono and uuid dependencies from kon-storage
- Add schema versioning TODO to run_migrations() for pre-release safety
- Add doc comment and usage example to log_error() (uncalled public API)
- Add TODO to consolidate app_data_dir() with model_manager::dirs_path()
- Add safety comments and #[allow(deprecated)] to keystore set_var usage
- Add TODO for keyring crate migration in cloud-providers keystore
- Apply cargo fmt

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/cloud-providers/src/keystore.rs

@@ -1,14 +1,29 @@
 /// Store an API key in the OS keychain.
-/// Stub implementation using environment variables until keyring crate is added.
+///
+/// Stub implementation using environment variables until the `keyring` crate is
+/// added. Keys are only held in-process and lost on exit.
+///
+/// # Safety note
+/// `std::env::set_var` is deprecated in Rust 2024 edition and is **not**
+/// thread-safe — mutating the environment while other threads read it is
+/// undefined behaviour. This is acceptable during single-threaded app init
+/// but must not be called from async/multi-threaded contexts.
+///
+/// TODO: Replace with the `keyring` crate (or platform-native credential
+/// storage) so keys persist across sessions and are accessed safely.
+#[allow(deprecated)] // set_var deprecated in Rust 2024 edition
 pub fn store_api_key(provider: &str, key: &str) {
-    std::env::set_var(
-        format!("KON_API_KEY_{}", provider.to_uppercase()),
-        key,
-    );
+    // SAFETY: Only safe when called from a single-threaded context (e.g. app
+    // initialisation). See doc comment above.
+    std::env::set_var(format!("KON_API_KEY_{}", provider.to_uppercase()), key);
 }
 
 /// Retrieve an API key from the OS keychain.
-/// Stub implementation using environment variables until keyring crate is added.
+///
+/// Stub implementation using environment variables until the `keyring` crate is
+/// added. Returns `None` if no key has been stored this session.
+///
+/// TODO: Replace with the `keyring` crate alongside `store_api_key`.
 pub fn retrieve_api_key(provider: &str) -> Option<String> {
     std::env::var(format!("KON_API_KEY_{}", provider.to_uppercase())).ok()
 }

crates/storage/Cargo.toml

@@ -12,9 +12,3 @@ sqlx = { version = "0.8", features = ["sqlite", "runtime-tokio"] }
 
 # Async runtime
 tokio = { version = "1", features = ["rt", "sync", "macros"] }
-
-# UUIDs for record IDs
-uuid = { version = "1", features = ["v4"] }
-
-# Timestamps
-chrono = { version = "0.4", features = ["serde"] }

crates/storage/src/database.rs

@@ -27,6 +27,11 @@ pub async fn init(db_path: &Path) -> Result<SqlitePool> {
 }
 
 /// Run schema migrations.
+///
+/// TODO(pre-release): Implement schema versioning for safe upgrades.
+/// Currently uses `CREATE TABLE IF NOT EXISTS` which silently ignores column
+/// additions/removals. Before shipping, add a `schema_version` table and
+/// sequential migration steps so existing user databases upgrade cleanly.
 async fn run_migrations(pool: &SqlitePool) -> Result<()> {
     sqlx::query(
         "CREATE TABLE IF NOT EXISTS transcripts (
@@ -186,10 +191,7 @@ pub async fn insert_transcript(
     Ok(())
 }
 
-pub async fn get_transcript(
-    pool: &SqlitePool,
-    id: &str,
-) -> Result<Option<TranscriptRow>> {
+pub async fn get_transcript(pool: &SqlitePool, id: &str) -> Result<Option<TranscriptRow>> {
     let row = sqlx::query(
         "SELECT id, text, source, title, audio_path, duration, engine, model_id, inference_ms, sample_rate, audio_channels, format_mode, remove_fillers, british_english, anti_hallucination, created_at FROM transcripts WHERE id = ?",
     )
@@ -231,16 +233,14 @@ pub async fn insert_task(
     bucket: &str,
     source_transcript_id: Option<&str>,
 ) -> Result<()> {
-    sqlx::query(
-        "INSERT INTO tasks (id, text, bucket, source_transcript_id) VALUES (?, ?, ?, ?)",
-    )
-    .bind(id)
-    .bind(text)
-    .bind(bucket)
-    .bind(source_transcript_id)
-    .execute(pool)
-    .await
-    .map_err(|e| KonError::StorageError(format!("Insert task failed: {e}")))?;
+    sqlx::query("INSERT INTO tasks (id, text, bucket, source_transcript_id) VALUES (?, ?, ?, ?)")
+        .bind(id)
+        .bind(text)
+        .bind(bucket)
+        .bind(source_transcript_id)
+        .execute(pool)
+        .await
+        .map_err(|e| KonError::StorageError(format!("Insert task failed: {e}")))?;
     Ok(())
 }
 
@@ -364,7 +364,19 @@ fn transcript_row_from(r: &sqlx::sqlite::SqliteRow) -> TranscriptRow {
 
 // --- Error Logging ---
 
-/// Log a structured error to the error_log table.
+/// Log a structured error to the `error_log` table.
+///
+/// Available for Tauri command handlers to persist errors for diagnostics.
+/// Each entry records context (which subsystem), an optional error code,
+/// the human-readable message, and optional JSON metadata.
+///
+/// # Example
+/// ```ignore
+/// log_error(&pool, "transcription", Some("WHISPER_INIT"), "Model load failed", None).await?;
+/// ```
+///
+/// TODO: Wire this into Tauri command error paths so runtime failures are
+/// persisted for user-facing error history and crash diagnostics.
 pub async fn log_error(
     pool: &SqlitePool,
     context: &str,

crates/storage/src/file_storage.rs

@@ -3,14 +3,16 @@ use std::path::PathBuf;
 /// Resolve the app data directory.
 /// Windows: %LOCALAPPDATA%/kon
 /// Unix: ~/.kon
+///
+/// TODO: Consolidate with `crates/transcription/src/model_manager.rs::dirs_path()`
+/// into a shared helper in `crates/core/` to avoid duplicating platform-specific
+/// path logic across crates.
 pub fn app_data_dir() -> PathBuf {
     if cfg!(target_os = "windows") {
-        let local_app_data =
-            std::env::var("LOCALAPPDATA").unwrap_or_else(|_| ".".to_string());
+        let local_app_data = std::env::var("LOCALAPPDATA").unwrap_or_else(|_| ".".to_string());
         PathBuf::from(local_app_data).join("kon")
     } else {
-        let home =
-            std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
+        let home = std::env::var("HOME").unwrap_or_else(|_| "/tmp".to_string());
         PathBuf::from(home).join(".kon")
     }
 }

crates/storage/src/lib.rs

@@ -2,8 +2,8 @@ pub mod database;
 pub mod file_storage;
 
 pub use database::{
-    complete_task, delete_task, delete_transcript, get_setting, get_transcript,
-    init, insert_task, insert_transcript, list_tasks, list_transcripts,
-    log_error, set_setting, InsertTranscriptParams, TaskRow, TranscriptRow,
+    complete_task, delete_task, delete_transcript, get_setting, get_transcript, init, insert_task,
+    insert_transcript, list_tasks, list_transcripts, log_error, set_setting,
+    InsertTranscriptParams, TaskRow, TranscriptRow,
 };
 pub use file_storage::{app_data_dir, database_path, recordings_dir};