feat: move checksumText to native

[RohitKushvaha01]

Related: #1803

[greptile-apps]

Greptile Summary

This PR offloads the checksumText function from a pure-JavaScript implementation (using the Web Crypto API and TextEncoder) to a native Android implementation via the existing Cordova System plugin. Both approaches produce identical SHA-256 hex output over UTF-8 bytes, so previously stored hashes in InstallState remain compatible and no data migration is needed.

Key changes:

• src/lib/installState.js: checksumText now delegates to cordova.exec("System", "checksumText", ...) instead of calling window.crypto.subtle.digest directly.
• System.java: A new checksumText switch case runs MessageDigest.getInstance("SHA-256") on the Cordova thread pool and returns the hex digest.
• A pre-existing missing break after the compare-texts case is also silently fixed (the fall-through to default: break was harmless but is now explicit).
• Three of the four new Java imports (org.apache.cordova.*, org.json.JSONArray, org.json.JSONException) are duplicates of imports already present at the top of the file; only java.security.MessageDigest is new.

Confidence Score: 4/5

• This PR is safe to merge; the logic is correct and the hash output is compatible with the old implementation.
• The core change is functionally correct — SHA-256 over UTF-8 bytes produces the same hex output in both the old JS and new Java paths, so no backward-compatibility issue exists for stored checksums. The identified issues are all style/hygiene concerns (duplicate imports, string-based charset literal, potential null error message) with no runtime impact in practice on Android where SHA-256 and UTF-8 are always available.
• The three duplicate imports in System.java (lines 110–113) should be cleaned up before merging to avoid import-section confusion in future edits.

Important Files Changed

Filename	Overview
src/lib/installState.js	Replaces the pure-JS checksumText implementation (Web Crypto API + TextEncoder) with a Cordova native bridge call to the new checksumText action on the System plugin. Both the old and new implementations produce identical SHA-256 hex output over UTF-8 bytes, so stored hashes remain compatible.
src/plugins/system/android/com/foxdebug/system/System.java	Adds the checksumText case to the switch dispatcher, running SHA-256 hashing on the thread pool and returning a hex string. Issues: three duplicate imports added (org.apache.cordova.*, JSONArray, JSONException already exist at lines 48–54); getBytes("UTF-8") should use StandardCharsets.UTF_8; e.getMessage() can return null.

Sequence Diagram

sequenceDiagram
    participant JS as installState.js
    participant Cordova as Cordova Bridge
    participant Java as System.java (Java)
    participant MD as MessageDigest (SHA-256)

    JS->>Cordova: cordova.exec("System", "checksumText", [text])
    Cordova->>Java: execute("checksumText", args, callbackContext)
    Java->>Java: cordova.getThreadPool().execute(lambda)
    Java->>MD: getInstance("SHA-256")
    MD-->>Java: digest instance
    Java->>MD: digest(text.getBytes("UTF-8"))
    MD-->>Java: byte[] hash
    Java->>Java: build hex string
    Java->>Cordova: callbackContext.success(hexString)
    Cordova-->>JS: resolve(hash)

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_{Last reviewed commit: 8465dcf}