feat(emacs): add org-caldav integration for Nextcloud calendar sync

- Enable org-caldav package in packages.el
- Configure base org-caldav settings (URL, timezone, sync behavior)
- Add Personal calendar two-way sync (~/org/personal-calendar.org)
- Add Tasks calendar one-way sync from todo.org
- Add keybinding SPC o C for manual sync
- Document setup requirements in config comments

Note: Conflict resolution is 'Org always wins' (org-caldav limitation).
User needs to create Nextcloud app password and ~/.authinfo.gpg.

Refs: x-5tb, x-5tb.1, x-5tb.2, x-5tb.3

home/roles/emacs/doom/config.el

@@ -83,15 +83,62 @@
        "d" #'org-agenda-day-view
        "w" #'org-agenda-week-view))
 
-;; (use-package! org-caldav
-;;   :defer t
-;;   :config
-;;   (setq org-caldav-url "https://nextcloud.johnogle.info/remote.php/dav/calendars/johno"
-;;         org-caldav-calendar-id "personal"
-;;         org-icalendar-timezone "America/Los_Angeles"
-;;         org-caldav-inbox "~/org/calendar.org"
-;;         org-caldav-files nil
-;;         org-caldav-sync-direction 'cal->org))
+;; org-caldav: Sync Org entries with Nextcloud CalDAV
+;; Setup requirements:
+;; 1. Create Nextcloud app password: Settings -> Security -> Devices & sessions
+;; 2. Store in rbw: rbw add nextcloud-caldav (username in notes, app password as secret)
+;; 3. Run: doom sync
+;; 4. Test: M-x org-caldav-sync
+;;
+;; Note: Conflict resolution is "Org always wins" - treat Org as source of truth
+;; for entries that originated in Org.
+(use-package! org-caldav
+  :after org
+  :commands (org-caldav-sync)
+  :init
+  (map! :leader
+        :desc "Sync calendar" "o C" #'org-caldav-sync)
+  :config
+  ;; Nextcloud CalDAV base URL
+  (setq org-caldav-url "https://nextcloud.johnogle.info/remote.php/dav/calendars/johno")
+
+  ;; Timezone for iCalendar export
+  (setq org-icalendar-timezone "America/Los_Angeles")
+
+  ;; Sync state storage (in org directory for multi-machine sync)
+  (setq org-caldav-save-directory (expand-file-name ".org-caldav/" org-directory))
+
+  ;; Backup file for entries before modification
+  (setq org-caldav-backup-file (expand-file-name ".org-caldav/backup.org" org-directory))
+
+  ;; Sync behavior: bidirectional by default
+  (setq org-caldav-sync-direction 'twoway)
+
+  ;; What changes from calendar sync back to Org (conservative: title and timestamp only)
+  (setq org-caldav-sync-changes-to-org 'title-and-timestamp)
+
+  ;; Deletion handling: ask before deleting
+  (setq org-caldav-delete-calendar-entries 'ask)
+  (setq org-caldav-delete-org-entries 'ask)
+
+  ;; Enable TODO/VTODO sync
+  (setq org-icalendar-include-todo 'all)
+  (setq org-caldav-sync-todo t)
+
+  ;; Calendar-specific configuration
+  (setq org-caldav-calendars
+        '(;; Personal calendar: two-way sync with family-shared Nextcloud calendar
+          (:calendar-id "personal"
+           :inbox "~/org/personal-calendar.org"
+           :files ("~/org/personal-calendar.org"))
+
+          ;; Tasks calendar: one-way sync (org → calendar only)
+          ;; SCHEDULED/DEADLINE items from todo.org push to private Tasks calendar.
+          ;; No inbox = no download from calendar (effectively one-way).
+          ;; Note: Create 'tasks' calendar in Nextcloud first, keep it private.
+          (:calendar-id "tasks"
+           :files ("~/org/todo.org"))))
+  )
 
 (defun my/get-rbw-password (alias)
   "Return the password for ALIAS via rbw, unlocking the vault only if needed."

home/roles/emacs/doom/packages.el

@@ -49,7 +49,7 @@
 ;; ...Or *all* packages (NOT RECOMMENDED; will likely break things)
 ;; (unpin! t)
 
-;; (package! org-caldav)
+(package! org-caldav)
 
 ;; Note: Packages with custom recipes must be pinned for nix-doom-emacs-unstraightened
 ;; to build deterministically. Update pins when upgrading packages.