Add curated support for photo invites

[BASIC-BIT]

Summary

Add curated support for VRChat photo invites.

The current unified/bulk invite work intentionally keeps photo invites out of scope because VRChat's photo invite endpoint uses multipart/form-data, while the generic generated write client JSON-serializes request bodies.

Context

VRChat exposes:

• POST /invite/{userId}/photo (inviteUserWithPhoto)
• POST /requestInvite/{userId}/photo (requestInviteWithPhoto)

The OpenAPI body shape is multipart:

• data: normal invite/request-invite payload
• image: PNG binary

Our generated write tooling is not enough for this because it sends JSON and sets content-type: application/json.

Proposed Scope

Add a curated photo invite implementation that:

• Accepts one target user initially; consider bulk using the same image after the single-target path is stable.
• Accepts users as either usr_... IDs or exact display names, matching the new curated invite behavior.
• Accepts destination using the same shape as vrchat_invite: here, full location, worldId + instanceId, or bare instanceId where valid.
• Accepts imagePath for a local PNG file.
• Reuses the invite message / overwriteMessageSlot flow where possible.
• Builds multipart/form-data directly instead of using the generic JSON write client.
• Returns structured per-target results if/when bulk support is added.

Acceptance Criteria

• Photo invite sends use multipart/form-data with data and image parts.
• Validation rejects missing/non-PNG/non-readable image paths with friendly guidance.
• Generated raw photo invite tools are either documented as not preferred or skipped in favor of curated tools.
• Tests cover multipart request construction without requiring a live VRChat call.
• Docs/tool catalog describe photo invite behavior and limitations.

Notes

Keep this separate from the first unified invite rollout so the core bulk/text invite path can stay mergeable without adding file upload complexity.