Add shared room creature catch flow

[halfdimension]

Adds backend-authoritative shared room creature catch flow.

• Adds catch endpoint for shared room creatures
• Validates room membership, running game state, expiry, duplicate catch, and catch distance
• Makes caught shared creatures disappear from the active room creature list
• Adds frontend shared creature catch action from map markers
• Shows catch success/error messages
• Verifies caught shared creatures disappear for other room members after refresh
• Keeps scoring, leaderboard updates, DB persistence, Redis, and WebSocket broadcasts out of scope
• Keeps solo gameplay unchanged