refactor: consolidate PNG encoder and safeParseJson utilities (#12457)

- Create shared PNG encoder module (src/media/png-encode.ts)

- Refactor qr-image.ts and live-image-probe.ts to use shared encoder

- Add safeParseJson to utils.ts and plugin-sdk exports

- Update msteams and pairing-store to use centralized safeParseJson

src/pairing/pairing-store.ts

@@ -7,6 +7,7 @@ import type { ChannelId, ChannelPairingAdapter } from "../channels/plugins/types
 import { getPairingAdapter } from "../channels/plugins/pairing.js";
 import { resolveOAuthDir, resolveStateDir } from "../config/paths.js";
 import { resolveRequiredHomeDir } from "../infra/home-dir.js";
+import { safeParseJson } from "../utils.js";
 
 const PAIRING_CODE_LENGTH = 8;
 const PAIRING_CODE_ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
@@ -72,14 +73,6 @@ function resolveAllowFromPath(
   return path.join(resolveCredentialsDir(env), `${safeChannelKey(channel)}-allowFrom.json`);
 }
 
-function safeParseJson<T>(raw: string): T | null {
-  try {
-    return JSON.parse(raw) as T;
-  } catch {
-    return null;
-  }
-}
-
 async function readJsonFile<T>(
   filePath: string,
   fallback: T,