Add .gitignore to .beads directory during init (#64)

- Create .gitignore file in .beads/ when running bd init
    - Ignores *.db and *.db-* patterns to prevent database commits
    - Add test coverage to verify .gitignore creation
    - Add .claude/settings.local.json to project .gitignore

    🤖 Generated with [Claude Code](https://claude.com/claude-code)

    Co-Authored-By: Claude <noreply@anthropic.com>

Co-authored-by: Ben Madore <madorb@users.noreply.github.com>

cmd/bd/init.go

@@ -42,6 +42,14 @@ and database file. Optionally specify a custom issue prefix.`,
 			os.Exit(1)
 		}
 
+		// Create .gitignore in .beads directory
+		gitignorePath := filepath.Join(beadsDir, ".gitignore")
+		gitignoreContent := "*.db\n*.db-*\n"
+		if err := os.WriteFile(gitignorePath, []byte(gitignoreContent), 0644); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: failed to create .gitignore: %v\n", err)
+			// Non-fatal - continue anyway
+		}
+
 		// Create database
 		dbPath := filepath.Join(beadsDir, prefix+".db")
 		store, err := sqlite.New(dbPath)

cmd/bd/testdata/init.txt

@@ -2,3 +2,6 @@
 bd init --prefix test
 stdout 'initialized successfully'
 exists .beads/test.db
+exists .beads/.gitignore
+grep '^\*\.db$' .beads/.gitignore
+grep '^\*\.db-\*$' .beads/.gitignore