feat(db): add channel_messages.raw_packet column for raw resend

Stores the full hex packet snapshot (header+transport_codes+path_len+payload)
captured at send time, enabling future "Resend (same packet hash)" feature
that lets repeaters deduplicate via Packet::calculatePacketHash while still
forwarding to nodes that didn't hear the original.

NULL for received and pre-migration rows (resend button stays disabled there).
PR #1 of 5; subsequent PRs wire up send-time capture, backend endpoint, echo
list merge, and UI.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/database.py

@@ -69,6 +69,12 @@ class Database:
             conn.execute("ALTER TABLE read_status ADD COLUMN is_favorite INTEGER DEFAULT 0")
             logger.info("Migration: added read_status.is_favorite column")
 
+        # Add raw_packet column to channel_messages (raw resend support)
+        cm_columns = {r[1] for r in conn.execute("PRAGMA table_info(channel_messages)").fetchall()}
+        if 'raw_packet' not in cm_columns:
+            conn.execute("ALTER TABLE channel_messages ADD COLUMN raw_packet TEXT")
+            logger.info("Migration: added channel_messages.raw_packet column")
+
     @contextmanager
     def _connect(self):
         """Yield a connection with auto-commit/rollback."""

app/schema.sql

@@ -86,6 +86,7 @@ CREATE TABLE IF NOT EXISTS channel_messages (
     snr                 REAL,
     path_len            INTEGER,
     pkt_payload         TEXT,                               -- for echo matching
+    raw_packet          TEXT,                               -- full hex packet (header+codes+path_len+payload) for raw resend; NULL for received/legacy rows
     raw_json            TEXT,                               -- original JSON line
     created_at          TEXT NOT NULL DEFAULT (datetime('now'))
 );