build: M1 Dockerized development stack with PHP skeleton, config/logging, Tailwind assets, and wrappers

Implements MeshVault M1 (issues #6–11):

- Four-service Docker Compose stack (nginx, PHP-FPM 8.3, PostgreSQL 17, Node assets)
- Slim 4 + PHP-DI routing with escaped PHP views and production/dev error handling
- Immutable validated AppConfig with redacted diagnostics
- JSON stdout Monolog logging with job-scoped context
- Tailwind CSS v4 deterministic locked builds with template scanning
- POSIX and PowerShell dev wrappers (up/down/test/lint/assets/watch)
- Startup config validation fails before FPM serves as unprivileged www-data
- migrate/seed explicitly unavailable until M2 (#12); #10 remains open

Verified via clean-start acceptance on remote host (keith@192.168.2.23).

.dockerignore

@@ -0,0 +1,14 @@
+# Explicit build inputs only: exclude secrets, collections and host dependencies.
+**
+!docker/
+!docker/php/
+!docker/php/**
+!composer.json
+!composer.lock
+!bin/
+!bin/**
+!docker/assets/
+!docker/assets/**
+!package.json
+!package-lock.json
+