feat: bump tier limits -- free 1 repo/10K fn, pro 5 repos, enterprise 10 (OPE-124)

Free tier: 3 repos/500 files/2K fn -> 1 repo/2K files/10K fn
  One repo, but make it count. Users can index a real codebase.
  10K functions covers Flask, Django, most mid-size projects.
  Cost: ~$0.04/user in embeddings. Negligible.

Pro tier: 20 repos -> 5 repos
  Focused. 5 repos is plenty for a team.

Enterprise tier: unlimited -> 10 repos
  Reasonable cap. Can increase per-customer.

Backend: user_limits.py TIER_LIMITS updated
Frontend: MAX_FREE_REPOS 3->1, TIER_FUNCTION_LIMITS free 2K->10K
UsagePage: CTA text updated to '5 repos'

Closes OPE-124

Author: DevanshuNEU

backend/services/user_limits.py

@@ -46,16 +46,16 @@ class TierLimits:
 # Tier definitions - Single source of truth
 TIER_LIMITS: Dict[UserTier, TierLimits] = {
     UserTier.FREE: TierLimits(
-        max_repos=3,
-        max_files_per_repo=500,
-        max_functions_per_repo=2000,
+        max_repos=1,
+        max_files_per_repo=2000,
+        max_functions_per_repo=10000,
         playground_searches_per_day=50,  # Generous, anti-abuse only
         max_team_members=1,
         priority_indexing=False,
         mcp_access=True,
     ),
     UserTier.PRO: TierLimits(
-        max_repos=20,
+        max_repos=5,
         max_files_per_repo=5000,
         max_functions_per_repo=20000,
         playground_searches_per_day=None,  # Unlimited
@@ -64,7 +64,7 @@ class TierLimits:
         mcp_access=True,
     ),
     UserTier.ENTERPRISE: TierLimits(
-        max_repos=None,  # Unlimited
+        max_repos=10,
         max_files_per_repo=50000,
         max_functions_per_repo=500000,
         playground_searches_per_day=None,

frontend/src/config/api.ts

@@ -59,11 +59,11 @@ export const buildWsUrl = (path: string): string => {
 }
 
 // free tier repo limit -- used in dashboard and GitHub import
-export const MAX_FREE_REPOS = 3
+export const MAX_FREE_REPOS = 1
 
-// function limits per tier -- used by DirectoryPicker budget bar
+// function limits per tier -- used by TopNav for tier validation
 export const TIER_FUNCTION_LIMITS = {
-  free: 2_000,
+  free: 10_000,
   pro: 20_000,
   enterprise: 500_000,
 } as const

frontend/src/pages/UsagePage.tsx

@@ -66,7 +66,7 @@ export function UsagePage() {
           <div>
             <p className="text-sm font-medium">Unlock higher limits and priority indexing</p>
             <p className="text-xs text-muted-foreground mt-0.5">
-              Pro: 20 repos, 20K functions/repo, Cohere reranking
+              Pro: 5 repos, 20K functions/repo, Cohere reranking
             </p>
           </div>
           <Button