[ci skip] Move Terraform modules into stack directories

Move all 88 service modules (66 individual + 22 platform) from
modules/kubernetes/<service>/ into their corresponding stack directories:

- Service stacks: stacks/<service>/module/
- Platform stack: stacks/platform/modules/<service>/

This collocates module source code with its Terragrunt definition.
Only shared utility modules remain in modules/kubernetes/:
ingress_factory, setup_tls_secret, dockerhub_secret, oauth-proxy.

All cross-references to shared modules updated to use correct
relative paths. Verified with terragrunt run --all -- plan:
0 adds, 0 destroys across all 68 stacks.

modules/kubernetes/dbaas/mysql_chart_values.yaml

@@ -1,14 +0,0 @@
----
-orchestrator:
-  # persistence:
-    # enabled: false
-  ingress:
-    enable: false
-    hosts:
-    - host: db.viktorbarzin.me
-      paths:
-      - path: /
-    tls:
-    - secretName: ${secretName}
-      hosts:
-        - db.viktorbarzin.me