Declare only the tables and columns pixa writes and reads (closes #310)

Removes output_content and request_cache, which nothing writes, and every
column that was written but never read: the host, path, query and
fetched_at of source_content, the content_type and created_at of
variant_content, and the status_code, error_message and fetched_at of
negative_cache.

StoreVariant no longer takes a content type and StoreNegative no longer
takes a status code or message, so extractStatusCode and the status
constants, which only fed status_code, are gone. Reconciliation adopts a
variant file without opening it, as its row no longer records a content
type. Tests that set or checked a removed column follow.

Model: opus-5-5

internal/imgcache/cache_internal_test.go

@@ -22,41 +22,15 @@ func setupTestDB(t *testing.T) *sql.DB {
 	schema := `
 		CREATE TABLE source_content (
 			source_key TEXT PRIMARY KEY,
-			source_host TEXT NOT NULL,
-			source_path TEXT NOT NULL,
-			source_query TEXT NOT NULL DEFAULT '',
 			content_type TEXT NOT NULL,
 			size_bytes INTEGER NOT NULL,
-			fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP,
 			last_accessed_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
 		);
-		CREATE TABLE output_content (
-			content_hash TEXT PRIMARY KEY,
-			content_type TEXT NOT NULL,
-			size_bytes INTEGER NOT NULL,
-			fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP
-		);
-		CREATE TABLE request_cache (
-			id INTEGER PRIMARY KEY AUTOINCREMENT,
-			cache_key TEXT NOT NULL UNIQUE,
-			source_metadata_id INTEGER NOT NULL,
-			output_hash TEXT NOT NULL,
-			width INTEGER NOT NULL,
-			height INTEGER NOT NULL,
-			format TEXT NOT NULL,
-			quality INTEGER NOT NULL DEFAULT 85,
-			fit_mode TEXT NOT NULL DEFAULT 'cover',
-			fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-			access_count INTEGER NOT NULL DEFAULT 1
-		);
 		CREATE TABLE negative_cache (
 			id INTEGER PRIMARY KEY AUTOINCREMENT,
 			source_host TEXT NOT NULL,
 			source_path TEXT NOT NULL,
 			source_query TEXT NOT NULL DEFAULT '',
-			status_code INTEGER NOT NULL,
-			error_message TEXT,
-			fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP,
 			expires_at DATETIME NOT NULL,
 			UNIQUE(source_host, source_path, source_query)
 		);
@@ -138,8 +112,8 @@ func TestCache_CleanExpired(t *testing.T) {
 	// Insert expired negative cache entry directly
 	_, err := db.ExecContext(ctx, `
 		INSERT INTO negative_cache
-			(source_host, source_path, source_query, status_code, expires_at)
-		VALUES ('example.com', '/old.jpg', '', 404, datetime('now', '-1 hour'))
+			(source_host, source_path, source_query, expires_at)
+		VALUES ('example.com', '/old.jpg', '', datetime('now', '-1 hour'))
 	`)
 	if err != nil {
 		t.Fatalf("failed to insert test data: %v", err)