Fix agent install/uninstall sudo placement, add dependency install hints

curl ... | API_URL=... bash runs as the invoking user, not root, so
"sudo" has to go right after the pipe (elevating bash) rather than
before curl — the old commands in the app UI, README, and scripts'
own usage comments put it in a spot that still failed the root check.
Also have install.sh/report-tasks.sh suggest the right package-manager
command (apt/dnf/yum/apk/pacman/zypper) when curl or jq is missing
instead of just failing, and bring the README up to date with both.

README.md

@@ -11,8 +11,9 @@ support is a documented future addition — see [`agent/windows/README.md`](agen
 
 - `server/` — Express + TypeScript API, SQLite (via libSQL) storage, Authentik OIDC login.
 - `web/` — React + Vite single-page app, served as static files by the Express server.
-- `agent/linux/` — `report-tasks.sh` (collects cron + systemd timer data) and
-  `install.sh` (installs it as a systemd timer on a target server).
+- `agent/linux/` — `report-tasks.sh` (collects cron + systemd timer data),
+  `install.sh` (installs it as a systemd timer on a target server), and
+  `uninstall.sh` (removes it).
 
 Data model, API contract, and sync behavior are documented in code:
 [`server/src/db/schema.ts`](server/src/db/schema.ts),
@@ -64,11 +65,13 @@ automatically on server start.
 
 1. Sign in, go to **Servers**, and add a server. The generated API token is
    shown once — copy it.
-2. On the target Linux server (as root):
+2. On the target Linux server, as root. If you're not already root, put
+   `sudo` right after the pipe so it elevates `bash`, not `curl` — `sudo curl
+   ... | bash` would still fail the root check:
 
    ```sh
    curl -fsSL https://schedule.example.lan/agent/linux/install.sh | \
-     API_URL=https://schedule.example.lan API_TOKEN=stm_xxx bash
+     sudo API_URL=https://schedule.example.lan API_TOKEN=stm_xxx bash
    ```
 
    This installs `report-tasks.sh` to `/usr/local/bin`, writes the API
@@ -76,7 +79,10 @@ automatically on server start.
    `schedule-task-manager-agent.timer` systemd timer that reports every 15
    minutes (override with `INTERVAL_MINUTES=5` before the `bash` above).
 
-   Requires `curl`, `jq`, and `systemd` on the target server.
+   Requires `curl`, `jq`, and `systemd` on the target server — if either
+   `curl` or `jq` is missing, both this script and `report-tasks.sh` print
+   the right install command for the server's package manager (apt, dnf,
+   yum, apk, pacman, or zypper) and exit.
 
 3. Tasks appear on the Dashboard, grouped by server and then by schedule type,
    within one reporting interval.
@@ -88,7 +94,7 @@ hidden by default — toggle "Show stale/missing tasks" to see them.
 To remove the agent from a server, run:
 
 ```sh
-curl -fsSL https://schedule.example.lan/agent/linux/uninstall.sh | bash
+curl -fsSL https://schedule.example.lan/agent/linux/uninstall.sh | sudo bash
 ```
 
 This stops and deletes the systemd timer/service, the installed script, and