feat: add Free subscription tier support (#8864)

## Summary

Add frontend support for a Free subscription tier — login/signup page
restructuring, telemetry instrumentation, and tier-aware billing gating.

## Changes

- **What**: 
- Restructure login/signup pages: OAuth buttons promoted as primary
sign-in method, email login available via progressive disclosure
- Add Free tier badge on Google sign-up button with dynamic credit count
from remote config
- Add `FREE` subscription tier to type system (tier pricing, tier rank,
registry types)
  - Add `isFreeTier` computed to `useSubscription()`
- Disable credit top-up for Free tier users (dialogService,
purchaseCredits, popover CTA)
- Show subscription/upgrade dialog instead of top-up dialog when Free
tier user hits out-of-credits
- Add funnel telemetry: `trackLoginOpened`, enrich `trackSignupOpened`
with `free_tier_badge_shown`, track email toggle clicks

## Review Focus

- Tier gating logic: Free tier users should see "Upgrade" instead of
"Add Credits" and never reach the top-up flow
- Telemetry event design for Mixpanel funnel analysis
- Progressive disclosure UX on login/signup pages

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8864-feat-add-Free-subscription-tier-support-3076d73d36508133b84ec5f0a67ccb03)
by [Unito](https://www.unito.io)

src/locales/en/main.json

@@ -1987,6 +1987,7 @@
       "newUser": "New here?",
       "userAvatar": "User Avatar",
       "signUp": "Sign up",
+      "signUpFreeTierPromo": "New here? {signUp} with Google to get {credits} free credits every month.",
       "emailLabel": "Email",
       "emailPlaceholder": "Enter your email",
       "passwordLabel": "Password",
@@ -2011,7 +2012,12 @@
       "failed": "Login failed",
       "insecureContextWarning": "This connection is insecure (HTTP) - your credentials may be intercepted by attackers if you proceed to login.",
       "questionsContactPrefix": "Questions? Contact us at",
-      "noAssociatedUser": "There is no Comfy user associated with the provided API key"
+      "noAssociatedUser": "There is no Comfy user associated with the provided API key",
+      "useEmailInstead": "Use email instead",
+      "freeTierBadge": "Eligible for Free Tier",
+      "freeTierDescription": "Sign up with Google to get {credits} free credits every month. No card needed.",
+      "freeTierDescriptionGeneric": "Sign up with Google to get free credits every month. No card needed.",
+      "backToSocialLogin": "Sign up with Google or Github instead"
     },
     "signup": {
       "title": "Create an account",
@@ -2025,7 +2031,8 @@
       "signUpWithGoogle": "Sign up with Google",
       "signUpWithGithub": "Sign up with Github",
       "regionRestrictionChina": "In accordance with local regulatory requirements, our services are temporarily unavailable to users located in China.",
-      "personalDataConsentLabel": "I agree to the processing of my personal data."
+      "personalDataConsentLabel": "I agree to the processing of my personal data.",
+      "emailNotEligibleForFreeTier": "Email sign-up is not eligible for Free Tier."
     },
     "signOut": {
       "signOut": "Log Out",
@@ -2216,10 +2223,15 @@
     "invoiceHistory": "Invoice history",
     "benefits": {
       "benefit1": "Monthly credits for Partner Nodes — top up when needed",
-      "benefit2": "Up to 30 min runtime per job"
+      "benefit1FreeTier": "More monthly credits, top up anytime",
+      "benefit2": "Up to 1 hour runtime per job on Pro",
+      "benefit3": "Bring your own models (Creator & Pro)"
     },
     "yearlyDiscount": "20% DISCOUNT",
     "tiers": {
+      "free": {
+        "name": "Free"
+      },
       "founder": {
         "name": "Founder's Edition"
       },
@@ -2253,6 +2265,21 @@
     "haveQuestions": "Have questions or wondering about enterprise?",
     "contactUs": "Contact us",
     "viewEnterprise": "View enterprise",
+    "freeTier": {
+      "title": "You're on the Free plan",
+      "description": "Your free plan includes {credits} credits each month to try Comfy Cloud.",
+      "descriptionGeneric": "Your free plan includes a monthly credit allowance to try Comfy Cloud.",
+      "nextRefresh": "Your credits refresh on {date}.",
+      "subscribeCta": "Subscribe for more",
+      "outOfCredits": {
+        "title": "You're out of free credits",
+        "subtitle": "Subscribe to unlock top-ups and more"
+      },
+      "topUpBlocked": {
+        "title": "Unlock top-ups and more"
+      },
+      "upgradeCta": "View plans"
+    },
     "partnerNodesCredits": "Partner nodes pricing",
     "plansAndPricing": "Plans & pricing",
     "managePlan": "Manage plan",
@@ -2280,6 +2307,7 @@
     "upgradeTo": "Upgrade to {plan}",
     "changeTo": "Change to {plan}",
     "maxDuration": {
+      "free": "30 min",
       "standard": "30 min",
       "creator": "30 min",
       "pro": "1 hr",