[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.

stacks/platform/modules/authentik/values.yaml

@@ -0,0 +1,31 @@
+authentik:
+  log_level: warning
+  # log_level: trace
+  secret_key: "${secret_key}"
+  # This sends anonymous usage-data, stack traces on errors and
+  # performance data to authentik.error-reporting.a7k.io, and is fully opt-in
+  error_reporting:
+    enabled: true
+  postgresql:
+    # host: postgresql.dbaas
+    host: pgbouncer.authentik
+    port: 6432
+    user: authentik
+    password: ${postgres_password}
+  redis:
+    host: redis.redis
+
+server:
+  replicas: 3
+  ingress:
+    enabled: false
+    # hosts:
+    #   - authentik.viktorbarzin.me
+  podAnnotations:
+    diun.enable: true
+    diun.include_tags: "^202[0-9].[0-9]+.*$" # no need to annotate the worker as it uses the same image
+global:
+  addPrometheusAnnotations: true
+
+worker:
+  replicas: 3