feat: add InsForge Go SDK

[Davidson3556]

Summary

• Add Go SDK with full feature parity to the existing JavaScript SDK
• Auth: sign up, sign in (password + OAuth), sign out, session refresh, profile management, email verification, password reset
• Database: fluent PostgREST-style query builder (select/insert/update/delete with filters), RPC calls, raw SQL
• Storage: upload (direct + S3 presigned multipart), download (direct + presigned), list, remove, public URLs
• AI: chat completions (streaming + non-streaming), embeddings, image generation
• Realtime: Socket.IO v4 WebSocket pub/sub with subscribe/publish/on/off/once
• Functions: serverless edge function invocation with configurable HTTP methods
• Email: transactional email sending

How did you test this change?

• Go unit tests (insforge/): net/http/httptest in-process server covering Auth (sign up success/error, sign in token storage, sign out), Database (SELECT, INSERT, RPC), and Storage (public URL, list, remove)
• Verified all endpoint paths and request/response field names against the JS SDK source and backend shared schemas
• Verified backend route handlers to confirm filter passing, auth middleware, and PostgREST proxy behavior

Note

Add InsForge Go SDK with auth, database, storage, AI, realtime, functions, and email modules

• Introduces a new Go module github.com/InsForge/insforge-go (Go 1.21) with a top-level Client that wires all service modules via a shared internal HTTP client.
• Adds Auth with full user lifecycle flows (sign-up, sign-in, OAuth, session refresh, password reset); Database with a PostgREST-style query builder (select, filter, insert, update, delete, RPC); and Storage with bucket-scoped upload, download, list, and delete.
• Adds AI with non-streaming and SSE streaming chat completions, embeddings, and image generation; Realtime using gorilla/websocket for pub/sub event handling; Functions for invoking edge functions; and Emails for sending transactional email.
• All modules share a common InsForgeError type and a generic Result[T] for structured responses.
• Basic tests for Auth, Database, and Storage are included using httptest servers.

^{Macroscope summarized 47c6c68.}

[Davidson3556]

@tonychang04 kindly review