[AZ-794] [AZ-795] [AZ-796] Strict input validation + z/x/y rename

AZ-794: rename inventory wire fields tileZoom/tileX/tileY -> z/x/y
to match the slippy-map URL convention. Contract bumped to v2.0.0.

AZ-795: shared validation infrastructure -- FluentValidation +
ValidationEndpointFilter + GlobalValidatorConfig (camelCase paths).
GlobalExceptionHandler now converts JsonException (UnmappedMember +
JsonRequired) into RFC 7807 ValidationProblemDetails. JSON layer
hardened with UnmappedMemberHandling.Disallow + camelCase naming
policy. New error-shape.md contract.

AZ-796: InventoryRequestValidator covers 9 rules (XOR tiles vs
locationHashes, cap 1000, z 0..22, x/y in slippy bounds, hash
length/charset). 16 unit tests + 16 integration tests + a manual
curl probe script.

Adjacent fixes uncovered by the new strict layer:
- IdempotentPostTests RoutePoint payload corrected to lat/lon
  (the DTO has used JsonPropertyName for ages; previously silently
  ignored under PascalCase fallback).
- TileInventoryTests slippy x/y reduced to fit z=18 bounds.
- docker-compose.yml host port for Postgres moved 5432 -> 5433 to
  avoid sibling-project conflict; appsettings.Development + README
  + AGENTS + architecture + containerization docs aligned.

New coderule (suite + repo): API consumer-facing OpenAPI
descriptions must not contain task IDs, contract filenames, or
version-bump history -- internal change tracking belongs in
commits/contract docs/changelogs. Existing offending descriptions
in Program.cs cleaned up.

Co-authored-by: Cursor <cursoragent@cursor.com>

SatelliteProvider.Api/Validators/GlobalValidatorConfig.cs

@@ -0,0 +1,31 @@
+using FluentValidation;
+
+namespace SatelliteProvider.Api.Validators;
+
+// AZ-795 / AZ-796: process-wide FluentValidation configuration shared by the
+// API host and unit tests. Tests must call ApplyOnce() in their fixture setup
+// so the property-name casing they assert against matches what the running
+// API will produce — see `_docs/02_document/contracts/api/error-shape.md`
+// invariant Inv-4 (camelCase paths in `errors` map).
+public static class GlobalValidatorConfig
+{
+    private static readonly object _gate = new();
+    private static bool _applied;
+
+    public static void ApplyOnce()
+    {
+        lock (_gate)
+        {
+            if (_applied) return;
+
+            ValidatorOptions.Global.PropertyNameResolver = (type, member, expression) =>
+            {
+                var name = member?.Name;
+                if (string.IsNullOrEmpty(name)) return null;
+                return char.ToLowerInvariant(name[0]) + name[1..];
+            };
+
+            _applied = true;
+        }
+    }
+}