[ci skip] Flatten module wrappers into stack roots

Remove the module "xxx" { source = "./module" } indirection layer
from all 66 service stacks. Resources are now defined directly in
each stack's main.tf instead of through a wrapper module.

- Merge module/main.tf contents into stack main.tf
- Apply variable replacements (var.tier -> local.tiers.X, renamed vars)
- Fix shared module paths (one fewer ../ at each level)
- Move extra files/dirs (factory/, chart_values, subdirs) to stack root
- Update state files to strip module.<name>. prefix
- Update CLAUDE.md to reflect flat structure

Verified: terragrunt plan shows 0 add, 0 destroy across all stacks.

stacks/f1-stream/module/files/internal/models/models.go

@@ -1,53 +0,0 @@
-package models
-
-import (
-	"time"
-
-	"github.com/go-webauthn/webauthn/webauthn"
-)
-
-type User struct {
-	ID          string                `json:"id"`
-	Username    string                `json:"username"`
-	IsAdmin     bool                  `json:"is_admin"`
-	Credentials []webauthn.Credential `json:"credentials"`
-	CreatedAt   time.Time             `json:"created_at"`
-}
-
-// WebAuthn interface implementation
-func (u *User) WebAuthnID() []byte                         { return []byte(u.ID) }
-func (u *User) WebAuthnName() string                       { return u.Username }
-func (u *User) WebAuthnDisplayName() string                { return u.Username }
-func (u *User) WebAuthnCredentials() []webauthn.Credential { return u.Credentials }
-
-type Stream struct {
-	ID          string    `json:"id"`
-	URL         string    `json:"url"`
-	Title       string    `json:"title"`
-	SubmittedBy string    `json:"submitted_by"`
-	Published   bool      `json:"published"`
-	Source      string    `json:"source"`
-	CreatedAt   time.Time `json:"created_at"`
-}
-
-type ScrapedLink struct {
-	ID        string    `json:"id"`
-	URL       string    `json:"url"`
-	Title     string    `json:"title"`
-	Source    string    `json:"source"`
-	ScrapedAt time.Time `json:"scraped_at"`
-	Stale     bool      `json:"stale"`
-}
-
-type Session struct {
-	Token     string    `json:"token"`
-	UserID    string    `json:"user_id"`
-	ExpiresAt time.Time `json:"expires_at"`
-}
-
-type HealthState struct {
-	URL                 string    `json:"url"`
-	ConsecutiveFailures int       `json:"consecutive_failures"`
-	LastCheckTime       time.Time `json:"last_check_time"`
-	Healthy             bool      `json:"healthy"`
-}