perf(daemon): add restart backoff, process priority, and map eviction

Supervisor had zero-delay restart on crash loops, pins CPU core at
100% if daemon keeps dying. Add exponential backoff (500ms to 30s cap,
resets after 30s stable). Set nice=10 on daemon child to yield CPU
to foreground apps. Evict stale entries from fileLocks and rate limiter
ConcurrentHashMaps that grew unbounded. Upload pre-built flashable zips
in CI instead of unpacking and re-compressing loose files.

app/src/main/cpp/supervisor.cpp

@@ -2,11 +2,13 @@
 #include <unistd.h>
 #include <sys/wait.h>
 #include <sys/prctl.h>
+#include <sys/resource.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
+#include <time.h>
 
 static volatile sig_atomic_t should_exit = 0;
 
@@ -27,7 +29,12 @@ int main(int argc, char *argv[]) {
     const char *daemon_path = argv[1];
     char **daemon_argv = &argv[1];
 
+    int backoff_ms = 500;
+
     while (!should_exit) {
+        struct timespec child_start;
+        clock_gettime(CLOCK_MONOTONIC, &child_start);
+
         pid_t pid = fork();
 
         if (pid < 0) {
@@ -39,6 +46,7 @@ int main(int argc, char *argv[]) {
         if (pid == 0) {
             // Child: become the daemon
             prctl(PR_SET_PDEATHSIG, SIGKILL); // Die if parent dies
+            setpriority(PRIO_PROCESS, 0, 10);  // lower CPU priority than foreground
             execv(daemon_path, daemon_argv);
             perror("execv failed");
             _exit(127);
@@ -50,7 +58,18 @@ int main(int argc, char *argv[]) {
 
         if (should_exit) break;
 
-        // Instant restart - no delay
+        // Exponential backoff on rapid crashes, reset if child was stable
+        struct timespec now;
+        clock_gettime(CLOCK_MONOTONIC, &now);
+        long lived_ms = (now.tv_sec - child_start.tv_sec) * 1000 +
+                        (now.tv_nsec - child_start.tv_nsec) / 1000000;
+
+        if (lived_ms > 30000) {
+            backoff_ms = 500;
+        } else {
+            usleep(backoff_ms * 1000);
+            if (backoff_ms < 30000) backoff_ms *= 2;
+        }
     }
 
     return 0;