[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>

AGENTS.md

@@ -177,7 +177,7 @@ docker-compose -f docker-compose.yml -f docker-compose.tests.yml up --build --ab
 ### Configuration Values
 
 Development defaults:
-- PostgreSQL: localhost:5432, user/pass: postgres/postgres
+- PostgreSQL: localhost:5433 (host-side, mapped to container port 5432), user/pass: postgres/postgres
 - API: http://localhost:5100
 - Max zoom level: 20
 - Default zoom level: 18