feat(java): serializers, middleware, dashboard, webhooks, CLI

[pratyush618]

Third of the Java SDK split series (follows #300). Adds cross-cutting infrastructure: serializers, middleware, the dashboard server, webhooks, and a CLI.

What's here

• Serializers (serialization/): SignedSerializer (HMAC-SHA256, 32-byte tag prefix, constant-time MessageDigest.isEqual) and EncryptedSerializer (AES-GCM, 12-byte IV prefix, 128-bit tag), each wrapping a delegate. JDK-only (javax.crypto).
• Middleware (middleware/): a Middleware interface with 8 default hooks (onEnqueue / before / after / onError / onCompleted / onRetry / onDeadLetter / onCancel) plus TaskContext / EnqueueContext (mutable payload + options). Queue.use(mw) registers it; the worker wraps each handler.
• Dashboard (dashboard/): DashboardServer over the JDK com.sun.net.httpserver, with a Contract mapper (camelCase → snake_case, Unix-ms, lowercase status) matching the cross-SDK dashboard API. Endpoints for stats / jobs / dead-letters / metrics / workers + cancel/retry/pause/resume; token auth; static SPA serving (path-traversal-guarded).
• Webhooks (webhooks/): WebhookManager implements Middleware and auto-dispatches matching lifecycle events to registered HTTP endpoints (java.net.http, X-Taskito-Signature: sha256=<hmac>, retry); CRUD persisted under a settings key.
• CLI (cli/): a picocli Cli with stats / enqueue / jobs / cancel / pause / resume / dlq / dashboard subcommands.

Scope

Pure-Java cross-cutting layers — no new native surface. Workflows, packaging, locks, ergonomics, etc. follow in later PRs. Targets Java 11.

Verification

Java compiles under --release 11 (main + tests DashboardTest/WebhookTest). The Rust workspace is covered by existing CI; the dedicated Java CI job arrives later in the series.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 423ca1da-f19b-4be3-859f-44f6120715b0

📥 Commits

Reviewing files that changed from the base of the PR and between b51f7a9 and 4dda0a8.

📒 Files selected for processing (24)

• sdks/java/README.md
• sdks/java/build.gradle.kts
• sdks/java/src/main/java/org/byteveda/taskito/DefaultQueue.java
• sdks/java/src/main/java/org/byteveda/taskito/Queue.java
• sdks/java/src/main/java/org/byteveda/taskito/Worker.java
• sdks/java/src/main/java/org/byteveda/taskito/WorkerDispatchBridge.java
• sdks/java/src/main/java/org/byteveda/taskito/cli/Cli.java
• sdks/java/src/main/java/org/byteveda/taskito/cli/package-info.java
• sdks/java/src/main/java/org/byteveda/taskito/dashboard/Contract.java
• sdks/java/src/main/java/org/byteveda/taskito/dashboard/DashboardServer.java
• sdks/java/src/main/java/org/byteveda/taskito/dashboard/package-info.java
• sdks/java/src/main/java/org/byteveda/taskito/middleware/EnqueueContext.java
• sdks/java/src/main/java/org/byteveda/taskito/middleware/Middleware.java
• sdks/java/src/main/java/org/byteveda/taskito/middleware/TaskContext.java
• sdks/java/src/main/java/org/byteveda/taskito/middleware/package-info.java
• sdks/java/src/main/java/org/byteveda/taskito/serialization/EncryptedSerializer.java
• sdks/java/src/main/java/org/byteveda/taskito/serialization/SignedSerializer.java
• sdks/java/src/main/java/org/byteveda/taskito/webhooks/Deliverer.java
• sdks/java/src/main/java/org/byteveda/taskito/webhooks/Webhook.java
• sdks/java/src/main/java/org/byteveda/taskito/webhooks/WebhookManager.java
• sdks/java/src/main/java/org/byteveda/taskito/webhooks/WebhookStore.java
• sdks/java/src/main/java/org/byteveda/taskito/webhooks/package-info.java
• sdks/java/src/test/java/org/byteveda/taskito/DashboardTest.java
• sdks/java/src/test/java/org/byteveda/taskito/WebhookTest.java

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/java-serializers-dashboard

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