feat(premium): cryptographic session verification for premium bypass

[Xephi]

Requirements

• PacketEvents must be installed on the server, unless you
  are using proxy mode (see "Behind a proxy" on docs/premium.md).

How it works

When a premium-enrolled player connects, AuthMe intercepts the Minecraft login handshake at
the packet level:

sequenceDiagram
    autonumber
    participant C as Client
    participant S as Server (AuthMe + PacketEvents)
    participant M as Mojang

    C->>S: LOGIN_START (name)
    Note over S: ① DB: isPremium → true (async)
    S->>C: ENCRYPTION_REQUEST (RSA-1024 Key + Random Token)
    
    rect rgb(240, 240, 240)
        Note right of C: Client starts encrypting outbound traffic
        C->>M: POST /session/minecraft/join
        C->>S: ENCRYPTION_RESPONSE (enc sharedSecret + Token)
    end

    Note over S: ② RSA-decrypt sharedSecret (sync/event-loop)
    Note over S: ③ Install AES/CFB8 Netty ciphers (sync, client sends encrypted from here)
    
    S->>M: ④ Verify token + GET /hasJoined (async)
    M-->>S: {uuid, name, properties}
    
    Note over S: ⑤ Store verified UUID (60s TTL)
    Note over S: ⑥ Re-inject LOGIN_START

    S->>C: Login Success

    rect rgb(230, 245, 230)
        Note over S: AsynchronousJoin: 
        Note over S: getVerifiedUuid(name) == auth.getPremiumUuid() -> Success / Auto-Login
    end

Loading

[TuxCoding]

I hope you don't mind my many comments :D

[TuxCoding]

I performed a CodeRabbit review in TuxCoding#14 and it found some noteworthy things. I copied the relevant things here.

[TuxCoding]

How did the translation files broke? :D

The pending verification looks good so far.

[lokspel]

if you are doing /premium then rejoin and login it says you're already logged in

[lokspel]

and what will happens if the license name will be changed, account will be locked?

[Xephi]

if you are doing /premium then rejoin and login it says you're already logged in

Should be fixed with ec5038a

and what will happens if the license name will be changed, account will be locked?

During the /premium process, you're kicked, you have to re-login to enable the premium feature completely. If you change your account name later, you'll may have to /login & /freemium + /premium again, but you won't be locked

[lokspel]

everything works
kick_reason: '&cНастройки Premium вашего аккаунта были изменены администратором. Пожалуйста, переподключитесь.'
but the kick reason for premium is not translated if the client is in russia

[lokspel]

we still use sessions even tho we dont need if we already use premium mode

[Xephi]

everything works kick_reason: '&cНастройки Premium вашего аккаунта были изменены администратором. Пожалуйста, переподключитесь.' but the kick reason for premium is not translated if the client is in russia

1b9f647

we still use sessions even tho we dont need if we already use premium mode

188c752

wah, can't write a good commit message anymore, time to sleep

[lokspel]

Why we store only online uuid in the db?
I think we should store offline as well in case if someone migrated from another plugin like https://github.com/whereareiam/Identica or nlogin with custom generated uuids

[lokspel]

Everything works now feel free to merge