Unified Ed25519 authentication - remove peer_id/credentials system

BREAKING CHANGE: Remove dual authentication system

- Remove POST /register endpoint - no longer needed
- Remove peer_id/secret credential-based auth
- All authentication now uses username + Ed25519 signatures
- Anonymous users can generate random usernames (anon-{timestamp}-{hex})

Database schema:
- Rename peer_id → username in offers table
- Rename answerer_peer_id → answerer_username in offers table
- Rename peer_id → username in ice_candidates table
- Remove secret column from offers table
- Add FK constraints for username columns

Storage layer:
- Update D1 and SQLite implementations
- All methods use username instead of peerId
- Remove secret-related code

Auth middleware:
- Replace validateCredentials() with Ed25519 signature verification
- Extract auth from request body (POST) or query params (GET)
- Verify signature against username's public key
- Validate message format and timestamp

Crypto utilities:
- Remove generatePeerId(), encryptPeerId(), decryptPeerId(), validateCredentials()
- Add generateAnonymousUsername() - creates anon-{timestamp}-{random}
- Add validateAuthMessage() - validates auth message format

Config:
- Remove authSecret from Config interface (no longer needed)

All server endpoints updated to use getAuthenticatedUsername()

migrations/fresh_schema.sql

@@ -1,4 +1,5 @@
--- Fresh schema for Rondevu v0.4.1+
+-- Fresh schema for Rondevu v0.5.0+
+-- Unified Ed25519 authentication - username/keypair only
 -- This is the complete schema without migration steps
 
 -- Drop existing tables if they exist
@@ -7,44 +8,7 @@ DROP TABLE IF EXISTS services;
 DROP TABLE IF EXISTS offers;
 DROP TABLE IF EXISTS usernames;
 
--- Offers table
-CREATE TABLE offers (
-  id TEXT PRIMARY KEY,
-  peer_id TEXT NOT NULL,
-  service_id TEXT,
-  sdp TEXT NOT NULL,
-  created_at INTEGER NOT NULL,
-  expires_at INTEGER NOT NULL,
-  last_seen INTEGER NOT NULL,
-  secret TEXT,
-  answerer_peer_id TEXT,
-  answer_sdp TEXT,
-  answered_at INTEGER
-);
-
-CREATE INDEX idx_offers_peer ON offers(peer_id);
-CREATE INDEX idx_offers_service ON offers(service_id);
-CREATE INDEX idx_offers_expires ON offers(expires_at);
-CREATE INDEX idx_offers_last_seen ON offers(last_seen);
-CREATE INDEX idx_offers_answerer ON offers(answerer_peer_id);
-
--- ICE candidates table
-CREATE TABLE ice_candidates (
-  id INTEGER PRIMARY KEY AUTOINCREMENT,
-  offer_id TEXT NOT NULL,
-  peer_id TEXT NOT NULL,
-  role TEXT NOT NULL CHECK(role IN ('offerer', 'answerer')),
-  candidate TEXT NOT NULL,
-  created_at INTEGER NOT NULL,
-  FOREIGN KEY (offer_id) REFERENCES offers(id) ON DELETE CASCADE
-);
-
-CREATE INDEX idx_ice_offer ON ice_candidates(offer_id);
-CREATE INDEX idx_ice_peer ON ice_candidates(peer_id);
-CREATE INDEX idx_ice_role ON ice_candidates(role);
-CREATE INDEX idx_ice_created ON ice_candidates(created_at);
-
--- Usernames table
+-- Usernames table (now required for all users, even anonymous)
 CREATE TABLE usernames (
   username TEXT PRIMARY KEY,
   public_key TEXT NOT NULL UNIQUE,
@@ -75,3 +39,43 @@ CREATE INDEX idx_services_fqn ON services(service_fqn);
 CREATE INDEX idx_services_discovery ON services(service_name, version);
 CREATE INDEX idx_services_username ON services(username);
 CREATE INDEX idx_services_expires ON services(expires_at);
+
+-- Offers table (now uses username instead of peer_id)
+CREATE TABLE offers (
+  id TEXT PRIMARY KEY,
+  username TEXT NOT NULL,
+  service_id TEXT,
+  service_fqn TEXT,
+  sdp TEXT NOT NULL,
+  created_at INTEGER NOT NULL,
+  expires_at INTEGER NOT NULL,
+  last_seen INTEGER NOT NULL,
+  answerer_username TEXT,
+  answer_sdp TEXT,
+  answered_at INTEGER,
+  FOREIGN KEY (username) REFERENCES usernames(username) ON DELETE CASCADE,
+  FOREIGN KEY (answerer_username) REFERENCES usernames(username) ON DELETE SET NULL
+);
+
+CREATE INDEX idx_offers_username ON offers(username);
+CREATE INDEX idx_offers_service ON offers(service_id);
+CREATE INDEX idx_offers_expires ON offers(expires_at);
+CREATE INDEX idx_offers_last_seen ON offers(last_seen);
+CREATE INDEX idx_offers_answerer ON offers(answerer_username);
+
+-- ICE candidates table (now uses username instead of peer_id)
+CREATE TABLE ice_candidates (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  offer_id TEXT NOT NULL,
+  username TEXT NOT NULL,
+  role TEXT NOT NULL CHECK(role IN ('offerer', 'answerer')),
+  candidate TEXT NOT NULL,
+  created_at INTEGER NOT NULL,
+  FOREIGN KEY (offer_id) REFERENCES offers(id) ON DELETE CASCADE,
+  FOREIGN KEY (username) REFERENCES usernames(username) ON DELETE CASCADE
+);
+
+CREATE INDEX idx_ice_offer ON ice_candidates(offer_id);
+CREATE INDEX idx_ice_username ON ice_candidates(username);
+CREATE INDEX idx_ice_role ON ice_candidates(role);
+CREATE INDEX idx_ice_created ON ice_candidates(created_at);