feat: replace strcpy/strcat with memcpy and add null-termination across multiple source files

Replace unsafe string concatenation patterns using strcpy/strcat with explicit memcpy calls and proper null-termination in bash_repair.c, context_manager.c, context_summarizer.c, and db.c. Add missing null-pointer checks for strdup results in bash_executor.c. Introduce atomic_int for spinner_running flag in http_client.c. Add consecutive_tool_error_iterations field to agent struct and refactor agent heartbeat/token tracking to use messages_get_db instead of db_open. Remove r_config_get_max_tokens declaration from r_config.h. Add json_repair.c to Makefile build sources and include db.h in messages.h with new messages_get_db function declaration.

Makefile

@@ -1,7 +1,7 @@
 # retoor <retoor@molodetz.nl>
 
 CC = gcc
-CFLAGS = -Ofast -Werror -Wall -I./include
+CFLAGS = -O3 -Werror -Wall -Wextra -Wshadow -I./include
 LDFLAGS = -lreadline -lncurses -lcurl -ljson-c -lsqlite3 -lm -lpthread -lssl -lcrypto
 
 SRCDIR = src
@@ -21,6 +21,7 @@ SRC_CORE = $(SRCDIR)/r_error.c \
            $(SRCDIR)/context_manager.c \
            $(SRCDIR)/markdown.c \
            $(SRCDIR)/r_diff.c \
+           $(SRCDIR)/json_repair.c \
            $(SRCDIR)/main.c
 
 SRC_TOOLS = $(TOOLSDIR)/tools_init.c \