i18n(zh-CN): complete and ship Simplified Chinese

- Translate the remaining 910 strings and review the whole catalog (meaning,
  terms, punctuation, label length) against the screens.
- Register zh-CN: any zh tag maps to it except Traditional ones (Hant, TW,
  HK, MO), which keep English until a Traditional catalog ships.
- Hemisphere letters get their own context so the HUD sector line reads
  21.33N, not a compass word; the Bhote Koshi imagery dates follow
  year-first languages (2021年10月16日).
- cjk.css: tight tracking for Chinese text and a 9px floor on the dock voice
  labels and layer buttons; Latin HUD readouts keep their look.
- docs/translations/zh-CN.md: style, plurals and glossary.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/i18n/same-as-english.json

@@ -98,6 +98,9 @@
     "fire confidence|nominal",
     "ft",
     "hPa",
+    "hemisphere|E",
+    "hemisphere|N",
+    "hemisphere|S",
     "installation class|BASE",
     "km",
     "km/h",
@@ -133,5 +136,60 @@
     "REC",
     "VS",
     "WHOT/BHOT"
+  ],
+  "zh-CN": [
+    "1090 MHz",
+    "978 MHz UAT",
+    "AIS: --",
+    "AIS: {name}",
+    "BRG {value}°",
+    "BRG —",
+    "CAL {value}",
+    "CAL · {badge}",
+    "CCTV",
+    "CRS {value}°",
+    "CRT",
+    "FLIR",
+    "FOV",
+    "FOV {value}°",
+    "FT",
+    "GEO",
+    "HDG",
+    "HDG {value}°",
+    "House",
+    "Ironbow",
+    "KTS",
+    "Landsat 8/9",
+    "MM",
+    "NVG",
+    "REC",
+    "SRC {value}",
+    "Sentinel-2",
+    "Techno",
+    "Trance",
+    "USB {rate} msg/s",
+    "WHOT/BHOT",
+    "dB",
+    "ft",
+    "hPa",
+    "hemisphere|E",
+    "hemisphere|N",
+    "hemisphere|S",
+    "hemisphere|W",
+    "km",
+    "km/h",
+    "kt",
+    "kts",
+    "mph",
+    "{city} CCTV",
+    "{rate} msg/s",
+    "{source} HTTP {status}",
+    "{speed} kn",
+    "{type}  SPD: {speed}  HDG: {heading}",
+    "{value} KM",
+    "{value} KM/S",
+    "ΔE",
+    "ΔN",
+    "▲ {frp} MW"
   ]
 }