fix: Enforce strict tier-based access control for node endpoints

Access control hierarchy:
- Anonymous (free): db-sync read-only ONLY, no node access
- Standard (≥50 TRP): db-sync + node read (UTxOs, protocol-params)
- Elevated (≥500 TRP): everything + tx submit
- Master: unrestricted

Node endpoints now return HTTP 403 for insufficient tier:
- GET /v1/address/{addr}/utxos → requires standard+
- GET /v1/protocol-params → requires standard+
- POST /v1/tx/submit → requires elevated+ (403 for standard/anonymous)

Added require_standard_tier and require_elevated_tier dependencies.

Dockerfile

@@ -5,7 +5,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     ca-certificates \
     libsodium23 \
-    libsecp256k1-1 \
     libnuma1 \
     && rm -rf /var/lib/apt/lists/*
 

main.py

@@ -8,10 +8,19 @@ Known policy IDs:
 - TRP: 9c4bd4a90cdb73d9ff681215ecf7dea9fb183d916d30487d17098e05
 - MAP: 24bd9e7b9ae3a61df79eca72fd8355d0f7767e4c55a04a0d919c019c
 
-TRP Gating Tiers:
-- 0 TRP → anonymous rate limits (20 req/min)
-- 50+ TRP → standard tier (100 req/min)
-- 500+ TRP → elevated tier (1000 req/min)
+Access Tiers (strictly enforced):
+- Anonymous (0 TRP, 20 req/min): 
+    db-sync read-only ONLY. Balance, transactions, tokens, blocks, assets, pools, sync status.
+    NO node access whatsoever.
+- Standard (≥50 TRP, 100 req/min):
+    db-sync read + node read-only. UTxO queries, protocol params.
+    NO transaction submission.
+- Elevated (≥500 TRP, 1000 req/min):
+    Everything above + POST /v1/tx/submit (transaction broadcasting).
+- Master key: Unrestricted access.
+
+Node endpoints (/v1/address/{addr}/utxos, /v1/protocol-params, /v1/tx/submit)
+return HTTP 403 for insufficient tier.
 """
 
 import os
@@ -520,6 +529,42 @@ async def require_master_key(auth: dict = Depends(get_auth_context)):
     return auth
 
 
+async def require_standard_tier(auth: dict = Depends(get_auth_context)):
+    """
+    Require standard tier or higher for node read endpoints.
+    Anonymous users get db-sync only - no direct node access.
+    """
+    if auth["tier"] == "anonymous":
+        raise HTTPException(
+            status_code=403,
+            detail={
+                "error": "tier_required",
+                "message": "Node access requires standard tier or higher (50+ TRP)",
+                "required_tier": "standard",
+                "current_tier": auth["tier"]
+            }
+        )
+    return auth
+
+
+async def require_elevated_tier(auth: dict = Depends(get_auth_context)):
+    """
+    Require elevated tier for transaction submission.
+    Standard tier gets read-only node access, elevated gets write.
+    """
+    if auth["tier"] not in ("elevated", "master"):
+        raise HTTPException(
+            status_code=403,
+            detail={
+                "error": "tier_required",
+                "message": "Transaction submission requires elevated tier (500+ TRP)",
+                "required_tier": "elevated",
+                "current_tier": auth["tier"]
+            }
+        )
+    return auth
+
+
 # ============ Middleware ============
 
 @app.middleware("http")
@@ -635,10 +680,13 @@ async def get_sync_status(auth: dict = Depends(get_auth_context)):
 # ============ Node Integration Endpoints ============
 
 @app.get("/v1/address/{address}/utxos")
-async def get_address_utxos(address: str, auth: dict = Depends(get_auth_context)):
+async def get_address_utxos(address: str, auth: dict = Depends(require_standard_tier)):
     """
     Query UTxOs for an address directly from the node.
     Faster than db-sync for current unspent outputs.
+    
+    Requires: standard tier (50+ TRP) or higher.
+    Anonymous users should use /v1/address/{address}/balance (db-sync) instead.
     """
     cache_key = f"utxos_{address}"
     cached = await get_cached(cache_key)
@@ -715,20 +763,18 @@ async def get_address_utxos(address: str, auth: dict = Depends(get_auth_context)
 @app.post("/v1/tx/submit")
 async def submit_transaction(
     request: TxSubmitRequest,
-    auth: dict = Depends(get_auth_context)
+    auth: dict = Depends(require_elevated_tier)
 ):
     """
     Submit a signed transaction to the network.
     Accepts hex or base64 encoded CBOR transaction.
+    
+    Requires: elevated tier (500+ TRP) or master key.
+    Standard tier gets read-only node access.
     """
-    # Check tx submission rate limit
+    # Check tx submission rate limit (elevated tier still has limits)
     allowed, retry_after = await check_rate_limit(auth["identifier"], auth["tier"], "tx_submit")
     if not allowed:
-        if auth["tier"] == "anonymous":
-            raise HTTPException(
-                status_code=403,
-                detail={"error": "forbidden", "message": "Transaction submission requires an API key"}
-            )
         raise HTTPException(
             status_code=429,
             detail={"error": "rate_limit_exceeded", "retry_after": retry_after}
@@ -808,10 +854,12 @@ async def submit_transaction(
 
 
 @app.get("/v1/protocol-params")
-async def get_protocol_params(auth: dict = Depends(get_auth_context)):
+async def get_protocol_params(auth: dict = Depends(require_standard_tier)):
     """
     Get current epoch protocol parameters from the node.
     Cached for 5 minutes.
+    
+    Requires: standard tier (50+ TRP) or higher.
     """
     global protocol_params_cache