fix: Add 'file:' prefix to SQLite URIs in doctor.go (#261)

Without the 'file:' URI scheme prefix, SQLite treats query parameters
like '?mode=ro' as part of the filename instead of connection options.
This caused:
- Creation of bogus files named 'beads.db?mode=ro'
- Failure to read database version from metadata table
- bd doctor incorrectly reporting 'version pre-0.17.5 (very old)'

Fixed two sql.Open() calls in doctor.go:
- Line 317 (checkIssueIDs function)
- Line 403 (getDatabaseVersionFromPath function)

Now uses 'file:'+dbPath+'?mode=ro' pattern consistent with migrate.go.

Fixes #260

Amp-Thread-ID: https://ampcode.com/threads/T-ac9832d6-15e4-4e25-8027-5e8b640b190b

Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/doctor.go

@@ -314,7 +314,7 @@ func checkIDFormat(path string) doctorCheck {
 	}
 
 	// Open database
-	db, err := sql.Open("sqlite3", dbPath+"?mode=ro")
+	db, err := sql.Open("sqlite3", "file:"+dbPath+"?mode=ro")
 	if err != nil {
 		return doctorCheck{
 			Name:    "Issue IDs",
@@ -400,7 +400,7 @@ func checkCLIVersion() doctorCheck {
 }
 
 func getDatabaseVersionFromPath(dbPath string) string {
-	db, err := sql.Open("sqlite3", dbPath+"?mode=ro")
+	db, err := sql.Open("sqlite3", "file:"+dbPath+"?mode=ro")
 	if err != nil {
 		return "unknown"
 	}