[Draft] Add durable generated short links for profiles, worlds, and events

[BASIC-BIT]

Problem

VRDex canonical slugs are readable, but profiles, worlds, and events may still benefit from permanent generated short links for sharing in chat, posters, QR codes, and compact embeds.

Scope

• define a generated short-code model for profiles, worlds, and events
• use a stable route such as /l/<code>
• start with a compact alphanumeric code length, likely six characters
• generate the code once and keep it permanently tied to the target record
• allow canonical slugs to remain editable without changing the generated short link
• define collision handling and reserved-code rules

Non-goals

• custom domains
• vanity short-code editing
• link analytics
• paid link tracking
• expiring links
• QR-code generation

Acceptance criteria

• profiles, worlds, and events have a durable short-link direction
• short links are distinct from editable canonical slugs
• generated codes have documented collision and reservation behavior
• /l/<code> routing behavior is clear enough for implementation
• the model avoids making future slug edits break already-shared links

Related

• [Draft] Add slug generation and uniqueness rules #10
• [Draft] Add core event model and CRUD flows #34
• [Draft][Epic] Add world discovery and creator attribution lane #79

[BASIC-BIT]

Follow-up issues filed from the v1.5 event automation triage:

• [Draft] Add Discord event post templating and publish/export workflow #121 may use durable event short links in Discord post templates.
• [Draft] Define restream and one-link event media control model #124 may use stable public watch/event links in restream or one-link routing workflows.

Linking here because generated short links are likely shared infrastructure for these later workflows.