feat: relay hardening — restore build, add tests, negentropy adapter

Restores build broken by eeb9d2d (cvm-relay-stability removed deps):
- CMakeLists.txt: restore display.c, font.c, local_relay.c, relay_selector.c, sync_manager.c, axs15231b, qrcode, wisp_relay
- tollgate_main.c: restore display.h, local_relay.h, relay_selector.h, sync_manager.h includes and display calls
- cvm_server.c: kept master's keepalive/timeout/ping-pong fixes

New test infrastructure:
- test-local-relay, test-relay-nip11, test-cvm-roundtrip, test-cvm-mcp, test-cross-board make targets
- test-cvm-roundtrip.mjs: MCP get_config + get_balance via public relay
- test-cross-board.mjs: cross-board payment test
- test-cvm-mcp-relay.mjs: kept from master

New unit tests (35 tests):
- test_display.c: 22 tests for escape_wifi_field
- test_negentropy_adapter.c: 13 tests for negentropy adapter

New modules:
- negentropy_adapter.c/h: NIP-77 adapter skeleton

Docs:
- AGENTS.md: display module docs, new test commands
- RELAY_HARDENING_PLAN.md: hardening checklist
- RELAY_HARDENING_MERGE.md: merge plan and checklist

Cleanup:
- Removed CHECKLIST-CVM-RELAY.md, PLAN-SQUASH-MERGE.md (stale planning docs)
- Removed components/esp-miner submodule

Host unit tests: 63/63 pass

1 files changed, 1 insertions, 1 deletions

diff --git a/main/display.c b/main/display.c
index 2b6cc88..72b7686 100644
--- a/main/display.c
+++ b/main/display.c
@@ -42,7 +42,7 @@ static int qr_pixel_size(int len) {
     return 2;
 }
 
-static int escape_wifi_field(const char *src, char *dst, int dst_size) {
+int escape_wifi_field(const char *src, char *dst, int dst_size) {
     int si = 0, di = 0;
     while (src[si] && di < dst_size - 2) {
         char c = src[si];