C ABI: full example suite + docs & About coverage (#224)

Stacked on #222 (base `feat/c-abi-hub`), so the diff is just the additions on top of the hub foundation — no merge of #222 required.

## What this adds

**Examples — full parity with rust/python/node (`examples/c/`)**
- `streaming.c` upgraded to the multi-indicator (SMA/EMA/RSI/MACD + signals) demo
- `backtest.c`, `multi_timeframe.c` (manual time-bucket resampling), `parallel_assets.c` (serial vs OpenMP fan-out, one handle per asset)
- three educational strategies: `strategy_rsi_mean_reversion.c`, `strategy_macd_adx.c`, `strategy_bollinger_squeeze.c`
- two network examples shelling out to `curl`: `fetch_btcusdt.c`, `live_binance.c` (REST poll)
- two header-only helpers (`wickra_csv.h`, `wickra_strategy.h`) since the C ABI ships no IO layer
- CMake builds all 11; the 9 offline ones run under `ctest` on 3 OS; the network two are built-only

**Docs & metadata — surface the C ABI everywhere it was missing**
- ARCHITECTURE diagram + crate table, SECURITY + THREAT_MODEL (the C ABI as the sole `unsafe` FFI surface), the three binding package READMEs, issue/PR templates, CHANGELOG, and the GitHub About template (live About + org description updated too)

**Cleanup**
- removed all references to the private generator tooling from public files (`bindings/c/src/lib.rs` header, `CONTRIBUTING.md`, `sync-about.yml`)

Verified locally: `cargo build -p wickra-c --release`, `cmake + ctest` (9/9 pass), and `-Wall -Wextra -Wpedantic` clean on gcc 13.

.github/workflows/sync-about.yml

@@ -42,10 +42,10 @@ name: Sync indicator count
 # single source of truth for what the bindings reach.
 #
 # Design: on PRs this workflow is a READ-ONLY check. The indicator wiring
-# (ScriptHelpers/_common.py wire_readme_counter) bumps both README.md and
-# docs/README.md inside the author's code commit, so the counter is already
-# correct by the time CI runs. If it is not, the check below fails loud and
-# asks the author to re-run the wiring — it never pushes a fix-up commit.
+# bumps both README.md and docs/README.md inside the author's code commit, so
+# the counter is already correct by the time CI runs. If it is not, the check
+# below fails loud and asks the author to re-run the wiring — it never pushes a
+# fix-up commit.
 #
 # (An earlier version pushed a GITHUB_TOKEN "sync indicator count" commit to
 # the PR head. Because GITHUB_TOKEN pushes trigger no workflows, that commit
@@ -149,7 +149,7 @@ jobs:
           # actually live (Cloudflare Pages, P8.1); merging this PR is therefore
           # gated on the domain resolving, otherwise the About link would 404.
           homepage="https://docs.wickra.org"
-          desc="Streaming-first technical indicators with a Rust core and Python, Node.js, and WebAssembly bindings. ${n} indicators, O(1) per-tick updates, no system dependencies. Drop-in TA-Lib replacement."
+          desc="Streaming-first technical indicators with a Rust core and Python, Node.js, WebAssembly, and C ABI bindings. ${n} indicators, O(1) per-tick updates, no system dependencies. Drop-in TA-Lib replacement."
           # Enforce the homepage unconditionally — it is a constant, so this both
           # corrects the stale kingchenc URL and self-heals any future drift.
           # Same Administration-write permission as --description (no extra scope).