Adds Pulicat Lake map (lagoon map with barrier island and two facing shores)

## Purpose

Adds Pulicat Lake, India's second-largest brackish lagoon, as a water-dominant two-shore map

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## Objectives

- Lagoon-centred map based on Pulicat Lake on the Andhra Pradesh / Tamil Nadu coast north of Chennai, including the Bay of Bengal coastline
- 12 Nations based on towns and villages (No additional nations, all use the existing `in` flag)
- 950k land area, 57% water. Almost exactly Caspian Sea's size (951k)
- Two facing shores split by the lagoon, plus the Sriharikota barrier spit dividing lagoon from open sea, so `special_team_count: 2` like Caspian Sea and Aegean
- Two island spawns inside the lagoon itself (Venadu, Irakkam) for asymmetric starts
- 1176x1872 (2.20MP) at 34 m/px, extent 40x63 km
- Source imagery OpenStreetMap (ODbL)

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## Description

Bounding box: W 80.0079, S 13.3923, E 80.3746, N 13.9633

Naval play runs on both sides of the barrier spit — the sheltered lagoon and the
open Bay of Bengal (21 km of sea at the north edge, 5 km at the south) — with the
spit and the lagoon mouth as the chokepoints between them.

Nations: Chittamur, Dugarajapatnam, Nelapattu, Sriharikota, Sullurpeta, Venadu,
Irakkam, Sunnambukulam, Annamalaicheri, Pulicat, Gummidipoondi, Thirupalaivanam

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## Assignment

- [x] I'd like to be assigned to this issue and work on it myself

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[Discord Name if Different]
phaniiiii